@@ -68,843 +68,867 @@ Settings Read from System Properties
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@@ -68,843 +68,867 @@ Settings Read from System Properties
Setting the Server Bind Address
Setting the Server Bind Address
@advanced_1023_a
@advanced_1023_a
Limitations
@advanced_1024_a
Glossary and Links
Glossary and Links
@advanced_1024_h2
@advanced_1025_h2
Result Sets
Result Sets
@advanced_1025_h3
@advanced_1026_h3
Limiting the Number of Rows
Limiting the Number of Rows
@advanced_1026_p
@advanced_1027_p
Before the result is returned to the application, all rows are read by the database. Server side cursors are not supported currently. If only the first few rows are interesting for the application, then the result set size should be limited to improve the performance. This can be done using LIMIT in a query (example: SELECT * FROM TEST LIMIT 100), or by using Statement.setMaxRows(max).
Before the result is returned to the application, all rows are read by the database. Server side cursors are not supported currently. If only the first few rows are interesting for the application, then the result set size should be limited to improve the performance. This can be done using LIMIT in a query (example: SELECT * FROM TEST LIMIT 100), or by using Statement.setMaxRows(max).
@advanced_1027_h3
@advanced_1028_h3
Large Result Sets and External Sorting
Large Result Sets and External Sorting
@advanced_1028_p
@advanced_1029_p
For result set larger than 1000 rows, the result is buffered to disk. If ORDER BY is used, the sorting is done using an external sort algorithm. In this case, each block of rows is sorted using quick sort, then written to disk; when reading the data, the blocks are merged together.
For result set larger than 1000 rows, the result is buffered to disk. If ORDER BY is used, the sorting is done using an external sort algorithm. In this case, each block of rows is sorted using quick sort, then written to disk; when reading the data, the blocks are merged together.
@advanced_1029_h2
@advanced_1030_h2
Large Objects
Large Objects
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@advanced_1031_h3
Storing and Reading Large Objects
Storing and Reading Large Objects
@advanced_1031_p
@advanced_1032_p
If it is possible that the objects don't fit into memory, then the data type CLOB (for textual data) or BLOB (for binary data) should be used. For these data types, the objects are not fully read into memory, by using streams. To store a BLOB, use PreparedStatement.setBinaryStream. To store a CLOB, use PreparedStatement.setCharacterStream. To read a BLOB, use ResultSet.getBinaryStream, and to read a CLOB, use ResultSet.getCharacterStream. If the client/server mode is used, the BLOB and CLOB data is fully read into memory when accessed. In this case, the size of a BLOB or CLOB is limited by the memory.
If it is possible that the objects don't fit into memory, then the data type CLOB (for textual data) or BLOB (for binary data) should be used. For these data types, the objects are not fully read into memory, by using streams. To store a BLOB, use PreparedStatement.setBinaryStream. To store a CLOB, use PreparedStatement.setCharacterStream. To read a BLOB, use ResultSet.getBinaryStream, and to read a CLOB, use ResultSet.getCharacterStream. If the client/server mode is used, the BLOB and CLOB data is fully read into memory when accessed. In this case, the size of a BLOB or CLOB is limited by the memory.
@advanced_1032_h2
@advanced_1033_h2
Linked Tables
Linked Tables
@advanced_1033_p
@advanced_1034_p
This database supports linked tables, which means tables that don't exist in the current database but are just links to another database. To create such a link, use the CREATE LINKED TABLE statement:
This database supports linked tables, which means tables that don't exist in the current database but are just links to another database. To create such a link, use the CREATE LINKED TABLE statement:
@advanced_1034_p
@advanced_1035_p
It is then possible to access the table in the usual way. There is a restriction when inserting data to this table: When inserting or updating rows into the table, NULL and values that are not set in the insert statement are both inserted as NULL. This may not have the desired effect if a default value in the target table is other than NULL.
It is then possible to access the table in the usual way. There is a restriction when inserting data to this table: When inserting or updating rows into the table, NULL and values that are not set in the insert statement are both inserted as NULL. This may not have the desired effect if a default value in the target table is other than NULL.
@advanced_1035_p
@advanced_1036_p
For each linked table a new connection is opened. This can be a problem for some databases when using many linked tables. For Oracle XE, the maximum number of connection can be increased. Oracle XE needs to be restarted after changing these values:
For each linked table a new connection is opened. This can be a problem for some databases when using many linked tables. For Oracle XE, the maximum number of connection can be increased. Oracle XE needs to be restarted after changing these values:
@advanced_1036_h2
@advanced_1037_h2
Transaction Isolation
Transaction Isolation
@advanced_1037_p
@advanced_1038_p
This database supports the following transaction isolation levels:
This database supports the following transaction isolation levels:
@advanced_1038_b
@advanced_1039_b
Read Committed
Read Committed
@advanced_1039_li
@advanced_1040_li
This is the default level. Read locks are released immediately. Higher concurrency is possible when using this level.
This is the default level. Read locks are released immediately. Higher concurrency is possible when using this level.
@advanced_1040_li
@advanced_1041_li
To enable, execute the SQL statement 'SET LOCK_MODE 3'
To enable, execute the SQL statement 'SET LOCK_MODE 3'
@advanced_1041_li
@advanced_1042_li
or append ;LOCK_MODE=3 to the database URL: jdbc:h2:~/test;LOCK_MODE=3
or append ;LOCK_MODE=3 to the database URL: jdbc:h2:~/test;LOCK_MODE=3
@advanced_1042_b
@advanced_1043_b
Serializable
Serializable
@advanced_1043_li
@advanced_1044_li
To enable, execute the SQL statement 'SET LOCK_MODE 1'
To enable, execute the SQL statement 'SET LOCK_MODE 1'
@advanced_1044_li
@advanced_1045_li
or append ;LOCK_MODE=1 to the database URL: jdbc:h2:~/test;LOCK_MODE=1
or append ;LOCK_MODE=1 to the database URL: jdbc:h2:~/test;LOCK_MODE=1
@advanced_1045_b
@advanced_1046_b
Read Uncommitted
Read Uncommitted
@advanced_1046_li
@advanced_1047_li
This level means that transaction isolation is disabled.
This level means that transaction isolation is disabled.
@advanced_1047_li
@advanced_1048_li
To enable, execute the SQL statement 'SET LOCK_MODE 0'
To enable, execute the SQL statement 'SET LOCK_MODE 0'
@advanced_1048_li
@advanced_1049_li
or append ;LOCK_MODE=0 to the database URL: jdbc:h2:~/test;LOCK_MODE=0
or append ;LOCK_MODE=0 to the database URL: jdbc:h2:~/test;LOCK_MODE=0
@advanced_1049_p
@advanced_1050_p
When using the isolation level 'serializable', dirty reads, non-repeatable reads, and phantom reads are prohibited.
When using the isolation level 'serializable', dirty reads, non-repeatable reads, and phantom reads are prohibited.
@advanced_1050_b
@advanced_1051_b
Dirty Reads
Dirty Reads
@advanced_1051_li
@advanced_1052_li
Means a connection can read uncommitted changes made by another connection.
Means a connection can read uncommitted changes made by another connection.
@advanced_1052_li
@advanced_1053_li
Possible with: read uncommitted
Possible with: read uncommitted
@advanced_1053_b
@advanced_1054_b
Non-Repeatable Reads
Non-Repeatable Reads
@advanced_1054_li
@advanced_1055_li
A connection reads a row, another connection changes a row and commits, and the first connection re-reads the same row and gets the new result.
A connection reads a row, another connection changes a row and commits, and the first connection re-reads the same row and gets the new result.
@advanced_1055_li
@advanced_1056_li
Possible with: read uncommitted, read committed
Possible with: read uncommitted, read committed
@advanced_1056_b
@advanced_1057_b
Phantom Reads
Phantom Reads
@advanced_1057_li
@advanced_1058_li
A connection reads a set of rows using a condition, another connection inserts a row that falls in this condition and commits, then the first connection re-reads using the same condition and gets the new row.
A connection reads a set of rows using a condition, another connection inserts a row that falls in this condition and commits, then the first connection re-reads using the same condition and gets the new row.
@advanced_1058_li
@advanced_1059_li
Possible with: read uncommitted, read committed
Possible with: read uncommitted, read committed
@advanced_1059_h3
@advanced_1060_h3
Table Level Locking
Table Level Locking
@advanced_1060_p
@advanced_1061_p
The database allows multiple concurrent connections to the same database. To make sure all connections only see consistent data, table level locking is used by default. This mechanism does not allow high concurrency, but is very fast. Shared locks and exclusive locks are supported. Before reading from a table, the database tries to add a shared lock to the table (this is only possible if there is no exclusive lock on the object by another connection). If the shared lock is added successfully, the table can be read. It is allowed that other connections also have a shared lock on the same object. If a connection wants to write to a table (update or delete a row), an exclusive lock is required. To get the exclusive lock, other connection must not have any locks on the object. After the connection commits, all locks are released. This database keeps all locks in memory.
The database allows multiple concurrent connections to the same database. To make sure all connections only see consistent data, table level locking is used by default. This mechanism does not allow high concurrency, but is very fast. Shared locks and exclusive locks are supported. Before reading from a table, the database tries to add a shared lock to the table (this is only possible if there is no exclusive lock on the object by another connection). If the shared lock is added successfully, the table can be read. It is allowed that other connections also have a shared lock on the same object. If a connection wants to write to a table (update or delete a row), an exclusive lock is required. To get the exclusive lock, other connection must not have any locks on the object. After the connection commits, all locks are released. This database keeps all locks in memory.
@advanced_1061_h3
@advanced_1062_h3
Lock Timeout
Lock Timeout
@advanced_1062_p
@advanced_1063_p
If a connection cannot get a lock on an object, the connection waits for some amount of time (the lock timeout). During this time, hopefully the connection holding the lock commits and it is then possible to get the lock. If this is not possible because the other connection does not release the lock for some time, the unsuccessful connection will get a lock timeout exception. The lock timeout can be set individually for each connection.
If a connection cannot get a lock on an object, the connection waits for some amount of time (the lock timeout). During this time, hopefully the connection holding the lock commits and it is then possible to get the lock. If this is not possible because the other connection does not release the lock for some time, the unsuccessful connection will get a lock timeout exception. The lock timeout can be set individually for each connection.
@advanced_1063_h2
@advanced_1064_h2
Multi-Version Concurrency Control (MVCC)
Multi-Version Concurrency Control (MVCC)
@advanced_1064_p
@advanced_1065_p
The MVCC feature allows higher concurrency than using (table level or row level) locks. When using MVCC in this database, delete, insert and update operations will only issue a shared lock on the table. An exclusive lock is still used when adding or removing columns, when dropping the table, and when using SELECT ... FOR UPDATE. Connections only 'see' committed data, and own changes. That means, if connection A updates a row but doesn't commit this change yet, connection B will see the old value. Only when the change is committed, the new value is visible by other connections (read committed). If multiple connections concurrently try to update the same row, this database fails fast: a concurrent update exception is thrown.
The MVCC feature allows higher concurrency than using (table level or row level) locks. When using MVCC in this database, delete, insert and update operations will only issue a shared lock on the table. An exclusive lock is still used when adding or removing columns, when dropping the table, and when using SELECT ... FOR UPDATE. Connections only 'see' committed data, and own changes. That means, if connection A updates a row but doesn't commit this change yet, connection B will see the old value. Only when the change is committed, the new value is visible by other connections (read committed). If multiple connections concurrently try to update the same row, this database fails fast: a concurrent update exception is thrown.
@advanced_1065_p
@advanced_1066_p
To use the MVCC feature, append MVCC=TRUE to the database URL:
To use the MVCC feature, append MVCC=TRUE to the database URL:
@advanced_1066_p
@advanced_1067_p
The MVCC feature is not fully tested yet.
The MVCC feature is not fully tested yet.
@advanced_1067_h2
@advanced_1068_h2
Clustering / High Availability
Clustering / High Availability
@advanced_1068_p
@advanced_1069_p
This database supports a simple clustering / high availability mechanism. The architecture is: two database servers run on two different computers, and on both computers is a copy of the same database. If both servers run, each database operation is executed on both computers. If one server fails (power, hardware or network failure), the other server can still continue to work. From this point on, the operations will be executed only on one server until the other server is back up.
This database supports a simple clustering / high availability mechanism. The architecture is: two database servers run on two different computers, and on both computers is a copy of the same database. If both servers run, each database operation is executed on both computers. If one server fails (power, hardware or network failure), the other server can still continue to work. From this point on, the operations will be executed only on one server until the other server is back up.
@advanced_1069_p
@advanced_1070_p
Clustering can only be used in the server mode (the embedded mode does not support clustering). It is possible to restore the cluster without stopping the server, however it is critical that no other application is changing the data in the first database while the second database is restored, so restoring the cluster is currently a manual process.
Clustering can only be used in the server mode (the embedded mode does not support clustering). It is possible to restore the cluster without stopping the server, however it is critical that no other application is changing the data in the first database while the second database is restored, so restoring the cluster is currently a manual process.
@advanced_1070_p
@advanced_1071_p
To initialize the cluster, use the following steps:
To initialize the cluster, use the following steps:
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@advanced_1072_li
Create a database
Create a database
@advanced_1072_li
@advanced_1073_li
Use the CreateCluster tool to copy the database to another location and initialize the clustering. Afterwards, you have two databases containing the same data.
Use the CreateCluster tool to copy the database to another location and initialize the clustering. Afterwards, you have two databases containing the same data.
@advanced_1073_li
@advanced_1074_li
Start two servers (one for each copy of the database)
Start two servers (one for each copy of the database)
@advanced_1074_li
@advanced_1075_li
You are now ready to connect to the databases with the client application(s)
You are now ready to connect to the databases with the client application(s)
@advanced_1075_h3
@advanced_1076_h3
Using the CreateCluster Tool
Using the CreateCluster Tool
@advanced_1076_p
@advanced_1077_p
To understand how clustering works, please try out the following example. In this example, the two databases reside on the same computer, but usually, the databases will be on different servers.
To understand how clustering works, please try out the following example. In this example, the two databases reside on the same computer, but usually, the databases will be on different servers.
@advanced_1077_li
@advanced_1078_li
Create two directories: server1 and server2. Each directory will simulate a directory on a computer.
Create two directories: server1 and server2. Each directory will simulate a directory on a computer.
@advanced_1078_li
@advanced_1079_li
Start a TCP server pointing to the first directory. You can do this using the command line:
Start a TCP server pointing to the first directory. You can do this using the command line:
@advanced_1079_li
@advanced_1080_li
Start a second TCP server pointing to the second directory. This will simulate a server running on a second (redundant) computer. You can do this using the command line:
Start a second TCP server pointing to the second directory. This will simulate a server running on a second (redundant) computer. You can do this using the command line:
@advanced_1080_li
@advanced_1081_li
Use the CreateCluster tool to initialize clustering. This will automatically create a new, empty database if it does not exist. Run the tool on the command line:
Use the CreateCluster tool to initialize clustering. This will automatically create a new, empty database if it does not exist. Run the tool on the command line:
@advanced_1081_li
@advanced_1082_li
You can now connect to the databases using an application or the H2 Console using the JDBC URL jdbc:h2:tcp://localhost:9101,localhost:9102/~/test
You can now connect to the databases using an application or the H2 Console using the JDBC URL jdbc:h2:tcp://localhost:9101,localhost:9102/~/test
@advanced_1082_li
@advanced_1083_li
If you stop a server (by killing the process), you will notice that the other machine continues to work, and therefore the database is still accessible.
If you stop a server (by killing the process), you will notice that the other machine continues to work, and therefore the database is still accessible.
@advanced_1083_li
@advanced_1084_li
To restore the cluster, you first need to delete the database that failed, then restart the server that was stopped, and re-run the CreateCluster tool.
To restore the cluster, you first need to delete the database that failed, then restart the server that was stopped, and re-run the CreateCluster tool.
@advanced_1084_h3
@advanced_1085_h3
Clustering Algorithm and Limitations
Clustering Algorithm and Limitations
@advanced_1085_p
@advanced_1086_p
Read-only queries are only executed against the first cluster node, but all other statements are executed against all nodes. There is currently no load balancing made to avoid problems with transactions. The following functions may yield different results on different cluster nodes and must be executed with care: RANDOM_UUID(), SECURE_RAND(), SESSION_ID(), MEMORY_FREE(), MEMORY_USED(), CSVREAD(), CSVWRITE(), RAND() [when not using a seed]. Those functions should not be used directly in modifying statements (for example INSERT, UPDATE, or MERGE). However, they can be used in read-only statements and the result can then be used for modifying statements.
Read-only queries are only executed against the first cluster node, but all other statements are executed against all nodes. There is currently no load balancing made to avoid problems with transactions. The following functions may yield different results on different cluster nodes and must be executed with care: RANDOM_UUID(), SECURE_RAND(), SESSION_ID(), MEMORY_FREE(), MEMORY_USED(), CSVREAD(), CSVWRITE(), RAND() [when not using a seed]. Those functions should not be used directly in modifying statements (for example INSERT, UPDATE, or MERGE). However, they can be used in read-only statements and the result can then be used for modifying statements.
@advanced_1086_h2
@advanced_1087_h2
Two Phase Commit
Two Phase Commit
@advanced_1087_p
@advanced_1088_p
The two phase commit protocol is supported. 2-phase-commit works as follows:
The two phase commit protocol is supported. 2-phase-commit works as follows:
@advanced_1088_li
@advanced_1089_li
Autocommit needs to be switched off
Autocommit needs to be switched off
@advanced_1089_li
@advanced_1090_li
A transaction is started, for example by inserting a row
A transaction is started, for example by inserting a row
@advanced_1090_li
@advanced_1091_li
The transaction is marked 'prepared' by executing the SQL statement <code>PREPARE COMMIT transactionName</code>
The transaction is marked 'prepared' by executing the SQL statement <code>PREPARE COMMIT transactionName</code>
@advanced_1091_li
@advanced_1092_li
The transaction can now be committed or rolled back
The transaction can now be committed or rolled back
@advanced_1092_li
@advanced_1093_li
If a problem occurs before the transaction was successfully committed or rolled back (for example because a network problem occurred), the transaction is in the state 'in-doubt'
If a problem occurs before the transaction was successfully committed or rolled back (for example because a network problem occurred), the transaction is in the state 'in-doubt'
@advanced_1093_li
@advanced_1094_li
When re-connecting to the database, the in-doubt transactions can be listed with <code>SELECT * FROM INFORMATION_SCHEMA.IN_DOUBT</code>
When re-connecting to the database, the in-doubt transactions can be listed with <code>SELECT * FROM INFORMATION_SCHEMA.IN_DOUBT</code>
@advanced_1094_li
@advanced_1095_li
Each transaction in this list must now be committed or rolled back by executing <code>COMMIT TRANSACTION transactionName</code> or <code>ROLLBACK TRANSACTION transactionName</code>
Each transaction in this list must now be committed or rolled back by executing <code>COMMIT TRANSACTION transactionName</code> or <code>ROLLBACK TRANSACTION transactionName</code>
@advanced_1095_li
@advanced_1096_li
The database needs to be closed and re-opened to apply the changes
The database needs to be closed and re-opened to apply the changes
@advanced_1096_h2
@advanced_1097_h2
Compatibility
Compatibility
@advanced_1097_p
@advanced_1098_p
This database is (up to a certain point) compatible to other databases such as HSQLDB, MySQL and PostgreSQL. There are certain areas where H2 is incompatible.
This database is (up to a certain point) compatible to other databases such as HSQLDB, MySQL and PostgreSQL. There are certain areas where H2 is incompatible.
@advanced_1098_h3
@advanced_1099_h3
Transaction Commit when Autocommit is On
Transaction Commit when Autocommit is On
@advanced_1099_p
@advanced_1100_p
At this time, this database engine commits a transaction (if autocommit is switched on) just before returning the result. For a query, this means the transaction is committed even before the application scans through the result set, and before the result set is closed. Other database engines may commit the transaction in this case when the result set is closed.
At this time, this database engine commits a transaction (if autocommit is switched on) just before returning the result. For a query, this means the transaction is committed even before the application scans through the result set, and before the result set is closed. Other database engines may commit the transaction in this case when the result set is closed.
@advanced_1100_h3
@advanced_1101_h3
Keywords / Reserved Words
Keywords / Reserved Words
@advanced_1101_p
@advanced_1102_p
There is a list of keywords that can't be used as identifiers (table names, column names and so on), unless they are quoted (surrounded with double quotes). The list is currently:
There is a list of keywords that can't be used as identifiers (table names, column names and so on), unless they are quoted (surrounded with double quotes). The list is currently:
@advanced_1102_p
@advanced_1103_p
CURRENT_TIMESTAMP, CURRENT_TIME, CURRENT_DATE, CROSS, DISTINCT, EXCEPT, EXISTS, FROM, FOR, FALSE, FULL, GROUP, HAVING, INNER, INTERSECT, IS, JOIN, LIKE, MINUS, NATURAL, NOT, NULL, ON, ORDER, PRIMARY, ROWNUM, SELECT, SYSDATE, SYSTIME, SYSTIMESTAMP, TODAY, TRUE, UNION, WHERE
CURRENT_TIMESTAMP, CURRENT_TIME, CURRENT_DATE, CROSS, DISTINCT, EXCEPT, EXISTS, FROM, FOR, FALSE, FULL, GROUP, HAVING, INNER, INTERSECT, IS, JOIN, LIKE, MINUS, NATURAL, NOT, NULL, ON, ORDER, PRIMARY, ROWNUM, SELECT, SYSDATE, SYSTIME, SYSTIMESTAMP, TODAY, TRUE, UNION, WHERE
@advanced_1103_p
@advanced_1104_p
Certain words of this list are keywords because they are functions that can be used without '()' for compatibility, for example CURRENT_TIMESTAMP.
Certain words of this list are keywords because they are functions that can be used without '()' for compatibility, for example CURRENT_TIMESTAMP.
@advanced_1104_h2
@advanced_1105_h2
Standards Compliance
Standards Compliance
@advanced_1105_p
@advanced_1106_p
This database tries to be as much standard compliant as possible. For the SQL language, ANSI/ISO is the main standard. There are several versions that refer to the release date: SQL-92, SQL:1999, and SQL:2003. Unfortunately, the standard documentation is not freely available. Another problem is that important features are not standardized. Whenever this is the case, this database tries to be compatible to other databases.
This database tries to be as much standard compliant as possible. For the SQL language, ANSI/ISO is the main standard. There are several versions that refer to the release date: SQL-92, SQL:1999, and SQL:2003. Unfortunately, the standard documentation is not freely available. Another problem is that important features are not standardized. Whenever this is the case, this database tries to be compatible to other databases.
@advanced_1106_h2
@advanced_1107_h2
Run as Windows Service
Run as Windows Service
@advanced_1107_p
@advanced_1108_p
Using a native wrapper / adapter, Java applications can be run as a Windows Service. There are various tools available to do that. The Java Service Wrapper from Tanuki Software, Inc. ( <a href="http://wrapper.tanukisoftware.org">http://wrapper.tanukisoftware.org</a> ) is included in the installation. Batch files are provided to install, start, stop and uninstall the H2 Database Engine Service. This service contains the TCP Server and the H2 Console web application. The batch files are located in the directory H2/service.
Using a native wrapper / adapter, Java applications can be run as a Windows Service. There are various tools available to do that. The Java Service Wrapper from Tanuki Software, Inc. ( <a href="http://wrapper.tanukisoftware.org">http://wrapper.tanukisoftware.org</a> ) is included in the installation. Batch files are provided to install, start, stop and uninstall the H2 Database Engine Service. This service contains the TCP Server and the H2 Console web application. The batch files are located in the directory H2/service.
@advanced_1108_h3
@advanced_1109_h3
Install the Service
Install the Service
@advanced_1109_p
@advanced_1110_p
The service needs to be registered as a Windows Service first. To do that, double click on 1_install_service.bat. If successful, a command prompt window will pop up and disappear immediately. If not, a message will appear.
The service needs to be registered as a Windows Service first. To do that, double click on 1_install_service.bat. If successful, a command prompt window will pop up and disappear immediately. If not, a message will appear.
@advanced_1110_h3
@advanced_1111_h3
Start the Service
Start the Service
@advanced_1111_p
@advanced_1112_p
You can start the H2 Database Engine Service using the service manager of Windows, or by double clicking on 2_start_service.bat. Please note that the batch file does not print an error message if the service is not installed.
You can start the H2 Database Engine Service using the service manager of Windows, or by double clicking on 2_start_service.bat. Please note that the batch file does not print an error message if the service is not installed.
@advanced_1112_h3
@advanced_1113_h3
Connect to the H2 Console
Connect to the H2 Console
@advanced_1113_p
@advanced_1114_p
After installing and starting the service, you can connect to the H2 Console application using a browser. Double clicking on 3_start_browser.bat to do that. The default port (8082) is hard coded in the batch file.
After installing and starting the service, you can connect to the H2 Console application using a browser. Double clicking on 3_start_browser.bat to do that. The default port (8082) is hard coded in the batch file.
@advanced_1114_h3
@advanced_1115_h3
Stop the Service
Stop the Service
@advanced_1115_p
@advanced_1116_p
To stop the service, double click on 4_stop_service.bat. Please note that the batch file does not print an error message if the service is not installed or started.
To stop the service, double click on 4_stop_service.bat. Please note that the batch file does not print an error message if the service is not installed or started.
@advanced_1116_h3
@advanced_1117_h3
Uninstall the Service
Uninstall the Service
@advanced_1117_p
@advanced_1118_p
To uninstall the service, double click on 5_uninstall_service.bat. If successful, a command prompt window will pop up and disappear immediately. If not, a message will appear.
To uninstall the service, double click on 5_uninstall_service.bat. If successful, a command prompt window will pop up and disappear immediately. If not, a message will appear.
@advanced_1118_h2
@advanced_1119_h2
ODBC Driver
ODBC Driver
@advanced_1119_p
@advanced_1120_p
This database does not come with its own ODBC driver at this time, but it supports the PostgreSQL network protocol. Therefore, the PostgreSQL ODBC driver can be used. Support for the PostgreSQL network protocol is quite new and should be viewed as experimental. It should not be used for production applications.
This database does not come with its own ODBC driver at this time, but it supports the PostgreSQL network protocol. Therefore, the PostgreSQL ODBC driver can be used. Support for the PostgreSQL network protocol is quite new and should be viewed as experimental. It should not be used for production applications.
@advanced_1120_p
@advanced_1121_p
At this time, the PostgreSQL ODBC driver does not work on 64 bit versions of Windows. For more information, see: <a href="http://svr5.postgresql.org/pgsql-odbc/2005-09/msg00127.php">ODBC Driver on Windows 64 bit</a>
At this time, the PostgreSQL ODBC driver does not work on 64 bit versions of Windows. For more information, see: <a href="http://svr5.postgresql.org/pgsql-odbc/2005-09/msg00127.php">ODBC Driver on Windows 64 bit</a>
@advanced_1121_h3
@advanced_1122_h3
ODBC Installation
ODBC Installation
@advanced_1122_p
@advanced_1123_p
First, the ODBC driver must be installed. Any recent PostgreSQL ODBC driver should work, however version 8.2.4 or newer is recommended. The Windows version of the PostgreSQL ODBC driver is available at <a href="http://www.postgresql.org/ftp/odbc/versions/msi">http://www.postgresql.org/ftp/odbc/versions/msi</a> .
First, the ODBC driver must be installed. Any recent PostgreSQL ODBC driver should work, however version 8.2.4 or newer is recommended. The Windows version of the PostgreSQL ODBC driver is available at <a href="http://www.postgresql.org/ftp/odbc/versions/msi">http://www.postgresql.org/ftp/odbc/versions/msi</a> .
@advanced_1123_h3
@advanced_1124_h3
Starting the Server
Starting the Server
@advanced_1124_p
@advanced_1125_p
After installing the ODBC driver, start the H2 Server using the command line:
After installing the ODBC driver, start the H2 Server using the command line:
@advanced_1125_p
@advanced_1126_p
The PG Server (PG for PostgreSQL protocol) is started as well. By default, databases are stored in the current working directory where the server is started. Use -baseDir to save databases in another directory, for example the user home directory:
The PG Server (PG for PostgreSQL protocol) is started as well. By default, databases are stored in the current working directory where the server is started. Use -baseDir to save databases in another directory, for example the user home directory:
@advanced_1126_p
@advanced_1127_p
The PG server can be started and stopped from within a Java application as follows:
The PG server can be started and stopped from within a Java application as follows:
@advanced_1127_p
@advanced_1128_p
By default, only connections from localhost are allowed. To allow remote connections, use <code>-pgAllowOthers true</code> when starting the server.
By default, only connections from localhost are allowed. To allow remote connections, use <code>-pgAllowOthers true</code> when starting the server.
@advanced_1128_h3
@advanced_1129_h3
ODBC Configuration
ODBC Configuration
@advanced_1129_p
@advanced_1130_p
After installing the driver, a new Data Source must be added. In Windows, run <code>odbcad32.exe</code> to open the Data Source Administrator. Then click on 'Add...' and select the PostgreSQL Unicode driver. Then click 'Finish'. You will be able to change the connection properties:
After installing the driver, a new Data Source must be added. In Windows, run <code>odbcad32.exe</code> to open the Data Source Administrator. Then click on 'Add...' and select the PostgreSQL Unicode driver. Then click 'Finish'. You will be able to change the connection properties:
@advanced_1130_th
@advanced_1131_th
Property
Property
@advanced_1131_th
@advanced_1132_th
Example
Example
@advanced_1132_th
@advanced_1133_th
Remarks
Remarks
@advanced_1133_td
@advanced_1134_td
Data Source
Data Source
@advanced_1134_td
@advanced_1135_td
H2 Test
H2 Test
@advanced_1135_td
@advanced_1136_td
The name of the ODBC Data Source
The name of the ODBC Data Source
@advanced_1136_td
@advanced_1137_td
Database
Database
@advanced_1137_td
@advanced_1138_td
test
test
@advanced_1138_td
@advanced_1139_td
The database name. Only simple names are supported at this time;
The database name. Only simple names are supported at this time;
@advanced_1139_td
@advanced_1140_td
relative or absolute path are not supported in the database name.
relative or absolute path are not supported in the database name.
@advanced_1140_td
@advanced_1141_td
By default, the database is stored in the current working directory
By default, the database is stored in the current working directory
@advanced_1141_td
@advanced_1142_td
where the Server is started except when the -baseDir setting is used.
where the Server is started except when the -baseDir setting is used.
@advanced_1142_td
@advanced_1143_td
The name must be at least 3 characters.
The name must be at least 3 characters.
@advanced_1143_td
@advanced_1144_td
Server
Server
@advanced_1144_td
@advanced_1145_td
localhost
localhost
@advanced_1145_td
@advanced_1146_td
The server name or IP address.
The server name or IP address.
@advanced_1146_td
@advanced_1147_td
By default, only remote connections are allowed
By default, only remote connections are allowed
@advanced_1147_td
@advanced_1148_td
User Name
User Name
@advanced_1148_td
@advanced_1149_td
sa
sa
@advanced_1149_td
@advanced_1150_td
The database user name.
The database user name.
@advanced_1150_td
@advanced_1151_td
SSL Mode
SSL Mode
@advanced_1151_td
@advanced_1152_td
disabled
disabled
@advanced_1152_td
@advanced_1153_td
At this time, SSL is not supported.
At this time, SSL is not supported.
@advanced_1153_td
@advanced_1154_td
Port
Port
@advanced_1154_td
@advanced_1155_td
5435
5435
@advanced_1155_td
@advanced_1156_td
The port where the PG Server is listening.
The port where the PG Server is listening.
@advanced_1156_td
@advanced_1157_td
Password
Password
@advanced_1157_td
@advanced_1158_td
sa
sa
@advanced_1158_td
@advanced_1159_td
The database password.
The database password.
@advanced_1159_p
@advanced_1160_p
Afterwards, you may use this data source.
Afterwards, you may use this data source.
@advanced_1160_h3
@advanced_1161_h3
PG Protocol Support Limitations
PG Protocol Support Limitations
@advanced_1161_p
@advanced_1162_p
At this time, only a subset of the PostgreSQL network protocol is implemented. Also, there may be compatibility problems on the SQL level, with the catalog, or with text encoding. Problems are fixed as they are found. Currently, statements can not be cancelled when using the PG protocol.
At this time, only a subset of the PostgreSQL network protocol is implemented. Also, there may be compatibility problems on the SQL level, with the catalog, or with text encoding. Problems are fixed as they are found. Currently, statements can not be cancelled when using the PG protocol.
@advanced_1162_p
@advanced_1163_p
PostgreSQL ODBC Driver Setup requires a database password; that means it is not possible to connect to H2 databases without password. This is a limitation of the ODBC driver.
PostgreSQL ODBC Driver Setup requires a database password; that means it is not possible to connect to H2 databases without password. This is a limitation of the ODBC driver.
@advanced_1163_h3
@advanced_1164_h3
Security Considerations
Security Considerations
@advanced_1164_p
@advanced_1165_p
Currently, the PG Server does not support challenge response or encrypt passwords. This may be a problem if an attacker can listen to the data transferred between the ODBC driver and the server, because the password is readable to the attacker. Also, it is currently not possible to use encrypted SSL connections. Therefore the ODBC driver should not be used where security is important.
Currently, the PG Server does not support challenge response or encrypt passwords. This may be a problem if an attacker can listen to the data transferred between the ODBC driver and the server, because the password is readable to the attacker. Also, it is currently not possible to use encrypted SSL connections. Therefore the ODBC driver should not be used where security is important.
@advanced_1165_h2
@advanced_1166_h2
Using H2 in Microsoft .NET
Using H2 in Microsoft .NET
@advanced_1166_p
@advanced_1167_p
The database can be used from Microsoft .NET even without using Java, by using IKVM.NET. You can access a H2 database on .NET using the JDBC API, or using the ADO.NET interface.
The database can be used from Microsoft .NET even without using Java, by using IKVM.NET. You can access a H2 database on .NET using the JDBC API, or using the ADO.NET interface.
@advanced_1167_h3
@advanced_1168_h3
Using the ADO.NET API on .NET
Using the ADO.NET API on .NET
@advanced_1168_p
@advanced_1169_p
An implementation of the ADO.NET interface is available in the open source project <a href="http://code.google.com/p/h2sharp">H2Sharp</a> .
An implementation of the ADO.NET interface is available in the open source project <a href="http://code.google.com/p/h2sharp">H2Sharp</a> .
@advanced_1169_h3
@advanced_1170_h3
Using the JDBC API on .NET
Using the JDBC API on .NET
@advanced_1170_li
@advanced_1171_li
Install the .NET Framework from <a href="http://www.microsoft.com">Microsoft</a> . Mono has not yet been tested.
Install the .NET Framework from <a href="http://www.microsoft.com">Microsoft</a> . Mono has not yet been tested.
Run the H2 Console using: <code>ikvm -jar h2.jar</code>
Run the H2 Console using: <code>ikvm -jar h2.jar</code>
@advanced_1174_li
@advanced_1175_li
Convert the H2 Console to an .exe file using: <code>ikvmc -target:winexe h2.jar</code> . You may ignore the warnings.
Convert the H2 Console to an .exe file using: <code>ikvmc -target:winexe h2.jar</code> . You may ignore the warnings.
@advanced_1175_li
@advanced_1176_li
Create a .dll file using (change the version accordingly): <code>ikvmc.exe -target:library -version:1.0.69.0 h2.jar</code>
Create a .dll file using (change the version accordingly): <code>ikvmc.exe -target:library -version:1.0.69.0 h2.jar</code>
@advanced_1176_p
@advanced_1177_p
If you want your C# application use H2, you need to add the h2.dll and the IKVM.OpenJDK.ClassLibrary.dll to your C# solution. Here some sample code:
If you want your C# application use H2, you need to add the h2.dll and the IKVM.OpenJDK.ClassLibrary.dll to your C# solution. Here some sample code:
@advanced_1177_h2
@advanced_1178_h2
ACID
ACID
@advanced_1178_p
@advanced_1179_p
In the database world, ACID stands for:
In the database world, ACID stands for:
@advanced_1179_li
@advanced_1180_li
Atomicity: Transactions must be atomic, meaning either all tasks are performed or none.
Atomicity: Transactions must be atomic, meaning either all tasks are performed or none.
@advanced_1180_li
@advanced_1181_li
Consistency: All operations must comply with the defined constraints.
Consistency: All operations must comply with the defined constraints.
@advanced_1181_li
@advanced_1182_li
Isolation: Transactions must be isolated from each other.
Isolation: Transactions must be isolated from each other.
@advanced_1182_li
@advanced_1183_li
Durability: Committed transaction will not be lost.
Durability: Committed transaction will not be lost.
@advanced_1183_h3
@advanced_1184_h3
Atomicity
Atomicity
@advanced_1184_p
@advanced_1185_p
Transactions in this database are always atomic.
Transactions in this database are always atomic.
@advanced_1185_h3
@advanced_1186_h3
Consistency
Consistency
@advanced_1186_p
@advanced_1187_p
This database is always in a consistent state. Referential integrity rules are always enforced.
This database is always in a consistent state. Referential integrity rules are always enforced.
@advanced_1187_h3
@advanced_1188_h3
Isolation
Isolation
@advanced_1188_p
@advanced_1189_p
For H2, as with most other database systems, the default isolation level is 'read committed'. This provides better performance, but also means that transactions are not completely isolated. H2 supports the transaction isolation levels 'serializable', 'read committed', and 'read uncommitted'.
For H2, as with most other database systems, the default isolation level is 'read committed'. This provides better performance, but also means that transactions are not completely isolated. H2 supports the transaction isolation levels 'serializable', 'read committed', and 'read uncommitted'.
@advanced_1189_h3
@advanced_1190_h3
Durability
Durability
@advanced_1190_p
@advanced_1191_p
This database does not guarantee that all committed transactions survive a power failure. Tests show that all databases sometimes lose transactions on power failure (for details, see below). Where losing transactions is not acceptable, a laptop or UPS (uninterruptible power supply) should be used. If durability is required for all possible cases of hardware failure, clustering should be used, such as the H2 clustering mode.
This database does not guarantee that all committed transactions survive a power failure. Tests show that all databases sometimes lose transactions on power failure (for details, see below). Where losing transactions is not acceptable, a laptop or UPS (uninterruptible power supply) should be used. If durability is required for all possible cases of hardware failure, clustering should be used, such as the H2 clustering mode.
@advanced_1191_h2
@advanced_1192_h2
Durability Problems
Durability Problems
@advanced_1192_p
@advanced_1193_p
Complete durability means all committed transaction survive a power failure. Some databases claim they can guarantee durability, but such claims are wrong. A durability test was run against H2, HSQLDB, PostgreSQL, and Derby. All of those databases sometimes lose committed transactions. The test is included in the H2 download, see org.h2.test.poweroff.Test.
Complete durability means all committed transaction survive a power failure. Some databases claim they can guarantee durability, but such claims are wrong. A durability test was run against H2, HSQLDB, PostgreSQL, and Derby. All of those databases sometimes lose committed transactions. The test is included in the H2 download, see org.h2.test.poweroff.Test.
@advanced_1193_h3
@advanced_1194_h3
Ways to (Not) Achieve Durability
Ways to (Not) Achieve Durability
@advanced_1194_p
@advanced_1195_p
Making sure that committed transactions are not lost is more complicated than it seems first. To guarantee complete durability, a database must ensure that the log record is on the hard drive before the commit call returns. To do that, databases use different methods. One is to use the 'synchronous write' file access mode. In Java, RandomAccessFile supports the modes "rws" and "rwd":
Making sure that committed transactions are not lost is more complicated than it seems first. To guarantee complete durability, a database must ensure that the log record is on the hard drive before the commit call returns. To do that, databases use different methods. One is to use the 'synchronous write' file access mode. In Java, RandomAccessFile supports the modes "rws" and "rwd":
@advanced_1195_li
@advanced_1196_li
rwd: Every update to the file's content is written synchronously to the underlying storage device.
rwd: Every update to the file's content is written synchronously to the underlying storage device.
@advanced_1196_li
@advanced_1197_li
rws: In addition to rwd, every update to the metadata is written synchronously.
rws: In addition to rwd, every update to the metadata is written synchronously.
@advanced_1197_p
@advanced_1198_p
This feature is used by Derby. A test (org.h2.test.poweroff.TestWrite) with one of those modes achieves around 50 thousand write operations per second. Even when the operating system write buffer is disabled, the write rate is around 50 thousand operations per second. This feature does not force changes to disk because it does not flush all buffers. The test updates the same byte in the file again and again. If the hard drive was able to write at this rate, then the disk would need to make at least 50 thousand revolutions per second, or 3 million RPM (revolutions per minute). There are no such hard drives. The hard drive used for the test is about 7200 RPM, or about 120 revolutions per second. There is an overhead, so the maximum write rate must be lower than that.
This feature is used by Derby. A test (org.h2.test.poweroff.TestWrite) with one of those modes achieves around 50 thousand write operations per second. Even when the operating system write buffer is disabled, the write rate is around 50 thousand operations per second. This feature does not force changes to disk because it does not flush all buffers. The test updates the same byte in the file again and again. If the hard drive was able to write at this rate, then the disk would need to make at least 50 thousand revolutions per second, or 3 million RPM (revolutions per minute). There are no such hard drives. The hard drive used for the test is about 7200 RPM, or about 120 revolutions per second. There is an overhead, so the maximum write rate must be lower than that.
@advanced_1198_p
@advanced_1199_p
Calling fsync flushes the buffers. There are two ways to do that in Java:
Calling fsync flushes the buffers. There are two ways to do that in Java:
@advanced_1199_li
@advanced_1200_li
FileDescriptor.sync(). The documentation says that this forces all system buffers to synchronize with the underlying device. Sync is supposed to return after all in-memory modified copies of buffers associated with this FileDescriptor have been written to the physical medium.
FileDescriptor.sync(). The documentation says that this forces all system buffers to synchronize with the underlying device. Sync is supposed to return after all in-memory modified copies of buffers associated with this FileDescriptor have been written to the physical medium.
@advanced_1200_li
@advanced_1201_li
FileChannel.force() (since JDK 1.4). This method is supposed to force any updates to this channel's file to be written to the storage device that contains it.
FileChannel.force() (since JDK 1.4). This method is supposed to force any updates to this channel's file to be written to the storage device that contains it.
@advanced_1201_p
@advanced_1202_p
By default, MySQL calls fsync for each commit. When using one of those methods, only around 60 write operations per second can be achieved, which is consistent with the RPM rate of the hard drive used. Unfortunately, even when calling FileDescriptor.sync() or FileChannel.force(), data is not always persisted to the hard drive, because most hard drives do not obey fsync(): see <a href="http://hardware.slashdot.org/article.pl?sid=05/05/13/0529252">Your Hard Drive Lies to You</a> . In Mac OS X, fsync does not flush hard drive buffers. See <a href="http://lists.apple.com/archives/darwin-dev/2005/Feb/msg00072.html">Bad fsync?</a> . So the situation is confusing, and tests prove there is a problem.
By default, MySQL calls fsync for each commit. When using one of those methods, only around 60 write operations per second can be achieved, which is consistent with the RPM rate of the hard drive used. Unfortunately, even when calling FileDescriptor.sync() or FileChannel.force(), data is not always persisted to the hard drive, because most hard drives do not obey fsync(): see <a href="http://hardware.slashdot.org/article.pl?sid=05/05/13/0529252">Your Hard Drive Lies to You</a> . In Mac OS X, fsync does not flush hard drive buffers. See <a href="http://lists.apple.com/archives/darwin-dev/2005/Feb/msg00072.html">Bad fsync?</a> . So the situation is confusing, and tests prove there is a problem.
@advanced_1202_p
@advanced_1203_p
Trying to flush hard drive buffers hard, and if you do the performance is very bad. First you need to make sure that the hard drive actually flushes all buffers. Tests show that this can not be done in a reliable way. Then the maximum number of transactions is around 60 per second. Because of those reasons, the default behavior of H2 is to delay writing committed transactions.
Trying to flush hard drive buffers hard, and if you do the performance is very bad. First you need to make sure that the hard drive actually flushes all buffers. Tests show that this can not be done in a reliable way. Then the maximum number of transactions is around 60 per second. Because of those reasons, the default behavior of H2 is to delay writing committed transactions.
@advanced_1203_p
@advanced_1204_p
In H2, after a power failure, a bit more than one second of committed transactions may be lost. To change the behavior, use SET WRITE_DELAY and CHECKPOINT SYNC. Most other databases support commit delay as well. In the performance comparison, commit delay was used for all databases that support it.
In H2, after a power failure, a bit more than one second of committed transactions may be lost. To change the behavior, use SET WRITE_DELAY and CHECKPOINT SYNC. Most other databases support commit delay as well. In the performance comparison, commit delay was used for all databases that support it.
@advanced_1204_h3
@advanced_1205_h3
Running the Durability Test
Running the Durability Test
@advanced_1205_p
@advanced_1206_p
To test the durability / non-durability of this and other databases, you can use the test application in the package org.h2.test.poweroff. Two computers with network connection are required to run this test. One computer just listens, while the test application is run (and power is cut) on the other computer. The computer with the listener application opens a TCP/IP port and listens for an incoming connection. The second computer first connects to the listener, and then created the databases and starts inserting records. The connection is set to 'autocommit', which means after each inserted record a commit is performed automatically. Afterwards, the test computer notifies the listener that this record was inserted successfully. The listener computer displays the last inserted record number every 10 seconds. Now, switch off the power manually, then restart the computer, and run the application again. You will find out that in most cases, none of the databases contains all the records that the listener computer knows about. For details, please consult the source code of the listener and test application.
To test the durability / non-durability of this and other databases, you can use the test application in the package org.h2.test.poweroff. Two computers with network connection are required to run this test. One computer just listens, while the test application is run (and power is cut) on the other computer. The computer with the listener application opens a TCP/IP port and listens for an incoming connection. The second computer first connects to the listener, and then created the databases and starts inserting records. The connection is set to 'autocommit', which means after each inserted record a commit is performed automatically. Afterwards, the test computer notifies the listener that this record was inserted successfully. The listener computer displays the last inserted record number every 10 seconds. Now, switch off the power manually, then restart the computer, and run the application again. You will find out that in most cases, none of the databases contains all the records that the listener computer knows about. For details, please consult the source code of the listener and test application.
@advanced_1206_h2
@advanced_1207_h2
Using the Recover Tool
Using the Recover Tool
@advanced_1207_p
@advanced_1208_p
The recover tool can be used to extract the contents of a data file, even if the database is corrupted. At this time, it does not extract the content of the log file or large objects (CLOB or BLOB). To run the tool, type on the command line:
The recover tool can be used to extract the contents of a data file, even if the database is corrupted. At this time, it does not extract the content of the log file or large objects (CLOB or BLOB). To run the tool, type on the command line:
@advanced_1208_p
@advanced_1209_p
For each database in the current directory, a text file will be created. This file contains raw insert statement (for the data) and data definition (DDL) statement to recreate the schema of the database. This file cannot be executed directly, as the raw insert statements don't have the correct table names, so the file needs to be pre-processed manually before executing.
For each database in the current directory, a text file will be created. This file contains raw insert statement (for the data) and data definition (DDL) statement to recreate the schema of the database. This file cannot be executed directly, as the raw insert statements don't have the correct table names, so the file needs to be pre-processed manually before executing.
@advanced_1209_h2
@advanced_1210_h2
File Locking Protocols
File Locking Protocols
@advanced_1210_p
@advanced_1211_p
Whenever a database is opened, a lock file is created to signal other processes that the database is in use. If database is closed, or if the process that opened the database terminates, this lock file is deleted.
Whenever a database is opened, a lock file is created to signal other processes that the database is in use. If database is closed, or if the process that opened the database terminates, this lock file is deleted.
@advanced_1211_p
@advanced_1212_p
In special cases (if the process did not terminate normally, for example because there was a blackout), the lock file is not deleted by the process that created it. That means the existence of the lock file is not a safe protocol for file locking. However, this software uses a challenge-response protocol to protect the database files. There are two methods (algorithms) implemented to provide both security (that is, the same database files cannot be opened by two processes at the same time) and simplicity (that is, the lock file does not need to be deleted manually by the user). The two methods are 'file method' and 'socket methods'.
In special cases (if the process did not terminate normally, for example because there was a blackout), the lock file is not deleted by the process that created it. That means the existence of the lock file is not a safe protocol for file locking. However, this software uses a challenge-response protocol to protect the database files. There are two methods (algorithms) implemented to provide both security (that is, the same database files cannot be opened by two processes at the same time) and simplicity (that is, the lock file does not need to be deleted manually by the user). The two methods are 'file method' and 'socket methods'.
@advanced_1212_h3
@advanced_1213_h3
File Locking Method 'File'
File Locking Method 'File'
@advanced_1213_p
@advanced_1214_p
The default method for database file locking is the 'File Method'. The algorithm is:
The default method for database file locking is the 'File Method'. The algorithm is:
@advanced_1214_li
@advanced_1215_li
When the lock file does not exist, it is created (using the atomic operation File.createNewFile). Then, the process waits a little bit (20ms) and checks the file again. If the file was changed during this time, the operation is aborted. This protects against a race condition when a process deletes the lock file just after one create it, and a third process creates the file again. It does not occur if there are only two writers.
When the lock file does not exist, it is created (using the atomic operation File.createNewFile). Then, the process waits a little bit (20ms) and checks the file again. If the file was changed during this time, the operation is aborted. This protects against a race condition when a process deletes the lock file just after one create it, and a third process creates the file again. It does not occur if there are only two writers.
@advanced_1215_li
@advanced_1216_li
If the file can be created, a random number is inserted together with the locking method ('file'). Afterwards, a watchdog thread is started that checks regularly (every second once by default) if the file was deleted or modified by another (challenger) thread / process. Whenever that occurs, the file is overwritten with the old data. The watchdog thread runs with high priority so that a change to the lock file does not get through undetected even if the system is very busy. However, the watchdog thread does use very little resources (CPU time), because it waits most of the time. Also, the watchdog only reads from the hard disk and does not write to it.
If the file can be created, a random number is inserted together with the locking method ('file'). Afterwards, a watchdog thread is started that checks regularly (every second once by default) if the file was deleted or modified by another (challenger) thread / process. Whenever that occurs, the file is overwritten with the old data. The watchdog thread runs with high priority so that a change to the lock file does not get through undetected even if the system is very busy. However, the watchdog thread does use very little resources (CPU time), because it waits most of the time. Also, the watchdog only reads from the hard disk and does not write to it.
@advanced_1216_li
@advanced_1217_li
If the lock file exists, and it was modified in the 20 ms, the process waits for some time (up to 10 times). If it was still changed, an exception is thrown (database is locked). This is done to eliminate race conditions with many concurrent writers. Afterwards, the file is overwritten with a new version (challenge). After that, the thread waits for 2 seconds. If there is a watchdog thread protecting the file, he will overwrite the change and this process will fail to lock the database. However, if there is no watchdog thread, the lock file will still be as written by this thread. In this case, the file is deleted and atomically created again. The watchdog thread is started in this case and the file is locked.
If the lock file exists, and it was modified in the 20 ms, the process waits for some time (up to 10 times). If it was still changed, an exception is thrown (database is locked). This is done to eliminate race conditions with many concurrent writers. Afterwards, the file is overwritten with a new version (challenge). After that, the thread waits for 2 seconds. If there is a watchdog thread protecting the file, he will overwrite the change and this process will fail to lock the database. However, if there is no watchdog thread, the lock file will still be as written by this thread. In this case, the file is deleted and atomically created again. The watchdog thread is started in this case and the file is locked.
@advanced_1217_p
@advanced_1218_p
This algorithm is tested with over 100 concurrent threads. In some cases, when there are many concurrent threads trying to lock the database, they block each other (meaning the file cannot be locked by any of them) for some time. However, the file never gets locked by two threads at the same time. However using that many concurrent threads / processes is not the common use case. Generally, an application should throw an error to the user if it cannot open a database, and not try again in a (fast) loop.
This algorithm is tested with over 100 concurrent threads. In some cases, when there are many concurrent threads trying to lock the database, they block each other (meaning the file cannot be locked by any of them) for some time. However, the file never gets locked by two threads at the same time. However using that many concurrent threads / processes is not the common use case. Generally, an application should throw an error to the user if it cannot open a database, and not try again in a (fast) loop.
@advanced_1218_h3
@advanced_1219_h3
File Locking Method 'Socket'
File Locking Method 'Socket'
@advanced_1219_p
@advanced_1220_p
There is a second locking mechanism implemented, but disabled by default. The algorithm is:
There is a second locking mechanism implemented, but disabled by default. The algorithm is:
@advanced_1220_li
@advanced_1221_li
If the lock file does not exist, it is created. Then a server socket is opened on a defined port, and kept open. The port and IP address of the process that opened the database is written into the lock file.
If the lock file does not exist, it is created. Then a server socket is opened on a defined port, and kept open. The port and IP address of the process that opened the database is written into the lock file.
@advanced_1221_li
@advanced_1222_li
If the lock file exists, and the lock method is 'file', then the software switches to the 'file' method.
If the lock file exists, and the lock method is 'file', then the software switches to the 'file' method.
@advanced_1222_li
@advanced_1223_li
If the lock file exists, and the lock method is 'socket', then the process checks if the port is in use. If the original process is still running, the port is in use and this process throws an exception (database is in use). If the original process died (for example due to a blackout, or abnormal termination of the virtual machine), then the port was released. The new process deletes the lock file and starts again.
If the lock file exists, and the lock method is 'socket', then the process checks if the port is in use. If the original process is still running, the port is in use and this process throws an exception (database is in use). If the original process died (for example due to a blackout, or abnormal termination of the virtual machine), then the port was released. The new process deletes the lock file and starts again.
@advanced_1223_p
@advanced_1224_p
This method does not require a watchdog thread actively polling (reading) the same file every second. The problem with this method is, if the file is stored on a network share, two processes (running on different computers) could still open the same database files, if they do not have a direct TCP/IP connection.
This method does not require a watchdog thread actively polling (reading) the same file every second. The problem with this method is, if the file is stored on a network share, two processes (running on different computers) could still open the same database files, if they do not have a direct TCP/IP connection.
@advanced_1224_h2
@advanced_1225_h2
Protection against SQL Injection
Protection against SQL Injection
@advanced_1225_h3
@advanced_1226_h3
What is SQL Injection
What is SQL Injection
@advanced_1226_p
@advanced_1227_p
This database engine provides a solution for the security vulnerability known as 'SQL Injection'. Here is a short description of what SQL injection means. Some applications build SQL statements with embedded user input such as:
This database engine provides a solution for the security vulnerability known as 'SQL Injection'. Here is a short description of what SQL injection means. Some applications build SQL statements with embedded user input such as:
@advanced_1227_p
@advanced_1228_p
If this mechanism is used anywhere in the application, and user input is not correctly filtered or encoded, it is possible for a user to inject SQL functionality or statements by using specially built input such as (in this example) this password: ' OR ''='. In this case the statement becomes:
If this mechanism is used anywhere in the application, and user input is not correctly filtered or encoded, it is possible for a user to inject SQL functionality or statements by using specially built input such as (in this example) this password: ' OR ''='. In this case the statement becomes:
@advanced_1228_p
@advanced_1229_p
Which is always true no matter what the password stored in the database is. For more information about SQL Injection, see Glossary and Links.
Which is always true no matter what the password stored in the database is. For more information about SQL Injection, see Glossary and Links.
@advanced_1229_h3
@advanced_1230_h3
Disabling Literals
Disabling Literals
@advanced_1230_p
@advanced_1231_p
SQL Injection is not possible if user input is not directly embedded in SQL statements. A simple solution for the problem above is to use a PreparedStatement:
SQL Injection is not possible if user input is not directly embedded in SQL statements. A simple solution for the problem above is to use a PreparedStatement:
@advanced_1231_p
@advanced_1232_p
This database provides a way to enforce usage of parameters when passing user input to the database. This is done by disabling embedded literals in SQL statements. To do this, execute the statement:
This database provides a way to enforce usage of parameters when passing user input to the database. This is done by disabling embedded literals in SQL statements. To do this, execute the statement:
@advanced_1232_p
@advanced_1233_p
Afterwards, SQL statements with text and number literals are not allowed any more. That means, SQL statement of the form WHERE NAME='abc' or WHERE CustomerId=10 will fail. It is still possible to use PreparedStatements and parameters as described above. Also, it is still possible to generate SQL statements dynamically, and use the Statement API, as long as the SQL statements do not include literals. There is also a second mode where number literals are allowed: SET ALLOW_LITERALS NUMBERS. To allow all literals, execute SET ALLOW_LITERALS ALL (this is the default setting). Literals can only be enabled or disabled by an administrator.
Afterwards, SQL statements with text and number literals are not allowed any more. That means, SQL statement of the form WHERE NAME='abc' or WHERE CustomerId=10 will fail. It is still possible to use PreparedStatements and parameters as described above. Also, it is still possible to generate SQL statements dynamically, and use the Statement API, as long as the SQL statements do not include literals. There is also a second mode where number literals are allowed: SET ALLOW_LITERALS NUMBERS. To allow all literals, execute SET ALLOW_LITERALS ALL (this is the default setting). Literals can only be enabled or disabled by an administrator.
@advanced_1233_h3
@advanced_1234_h3
Using Constants
Using Constants
@advanced_1234_p
@advanced_1235_p
Disabling literals also means disabling hard-coded 'constant' literals. This database supports defining constants using the CREATE CONSTANT command. Constants can be defined only when literals are enabled, but used even when literals are disabled. To avoid name clashes with column names, constants can be defined in other schemas:
Disabling literals also means disabling hard-coded 'constant' literals. This database supports defining constants using the CREATE CONSTANT command. Constants can be defined only when literals are enabled, but used even when literals are disabled. To avoid name clashes with column names, constants can be defined in other schemas:
@advanced_1235_p
@advanced_1236_p
Even when literals are enabled, it is better to use constants instead of hard-coded number or text literals in queries or views. With constants, typos are found at compile time, the source code is easier to understand and change.
Even when literals are enabled, it is better to use constants instead of hard-coded number or text literals in queries or views. With constants, typos are found at compile time, the source code is easier to understand and change.
@advanced_1236_h3
@advanced_1237_h3
Using the ZERO() Function
Using the ZERO() Function
@advanced_1237_p
@advanced_1238_p
It is not required to create a constant for the number 0 as there is already a built-in function ZERO():
It is not required to create a constant for the number 0 as there is already a built-in function ZERO():
@advanced_1238_h2
@advanced_1239_h2
Restricting Class Loading and Usage
Restricting Class Loading and Usage
@advanced_1239_p
@advanced_1240_p
By default there is no restriction on loading classes and executing Java code for admins. That means an admin may call system functions such as System.setProperty by executing:
By default there is no restriction on loading classes and executing Java code for admins. That means an admin may call system functions such as System.setProperty by executing:
@advanced_1240_p
@advanced_1241_p
To restrict users (including admins) from loading classes and executing code, the list of allowed classes can be set in the system property h2.allowedClasses in the form of a comma separated list of classes or patterns (items ending with '*'). By default all classes are allowed. Example:
To restrict users (including admins) from loading classes and executing code, the list of allowed classes can be set in the system property h2.allowedClasses in the form of a comma separated list of classes or patterns (items ending with '*'). By default all classes are allowed. Example:
@advanced_1241_p
@advanced_1242_p
This mechanism is used for all user classes, including database event listeners, trigger classes, user-defined functions, user-defined aggregate functions, and JDBC driver classes (with the exception of the H2 driver) when using the H2 Console.
This mechanism is used for all user classes, including database event listeners, trigger classes, user-defined functions, user-defined aggregate functions, and JDBC driver classes (with the exception of the H2 driver) when using the H2 Console.
@advanced_1242_h2
@advanced_1243_h2
Security Protocols
Security Protocols
@advanced_1243_p
@advanced_1244_p
The following paragraphs document the security protocols used in this database. These descriptions are very technical and only intended for security experts that already know the underlying security primitives.
The following paragraphs document the security protocols used in this database. These descriptions are very technical and only intended for security experts that already know the underlying security primitives.
@advanced_1244_h3
@advanced_1245_h3
User Password Encryption
User Password Encryption
@advanced_1245_p
@advanced_1246_p
When a user tries to connect to a database, the combination of user name, @, and password hashed using SHA-256, and this hash value is transmitted to the database. This step does not try to an attacker from re-using the value if he is able to listen to the (unencrypted) transmission between the client and the server. But, the passwords are never transmitted as plain text, even when using an unencrypted connection between client and server. That means if a user reuses the same password for different things, this password is still protected up to some point. See also 'RFC 2617 - HTTP Authentication: Basic and Digest Access Authentication' for more information.
When a user tries to connect to a database, the combination of user name, @, and password hashed using SHA-256, and this hash value is transmitted to the database. This step does not try to an attacker from re-using the value if he is able to listen to the (unencrypted) transmission between the client and the server. But, the passwords are never transmitted as plain text, even when using an unencrypted connection between client and server. That means if a user reuses the same password for different things, this password is still protected up to some point. See also 'RFC 2617 - HTTP Authentication: Basic and Digest Access Authentication' for more information.
@advanced_1246_p
@advanced_1247_p
When a new database or user is created, a new cryptographically secure random salt value is generated. The size of the salt is 64 bit. Using the random salt reduces the risk of an attacker pre-calculating hash values for many different (commonly used) passwords.
When a new database or user is created, a new cryptographically secure random salt value is generated. The size of the salt is 64 bit. Using the random salt reduces the risk of an attacker pre-calculating hash values for many different (commonly used) passwords.
@advanced_1247_p
@advanced_1248_p
The combination of user-password hash value (see above) and salt is hashed using SHA-256. The resulting value is stored in the database. When a user tries to connect to the database, the database combines user-password hash value with the stored salt value and calculated the hash value. Other products use multiple iterations (hash the hash value again and again), but this is not done in this product to reduce the risk of denial of service attacks (where the attacker tries to connect with bogus passwords, and the server spends a lot of time calculating the hash value for each password). The reasoning is: if the attacker has access to the hashed passwords, he also has access to the data in plain text, and therefore does not need the password any more. If the data is protected by storing it on another computer and only remotely, then the iteration count is not required at all.
The combination of user-password hash value (see above) and salt is hashed using SHA-256. The resulting value is stored in the database. When a user tries to connect to the database, the database combines user-password hash value with the stored salt value and calculated the hash value. Other products use multiple iterations (hash the hash value again and again), but this is not done in this product to reduce the risk of denial of service attacks (where the attacker tries to connect with bogus passwords, and the server spends a lot of time calculating the hash value for each password). The reasoning is: if the attacker has access to the hashed passwords, he also has access to the data in plain text, and therefore does not need the password any more. If the data is protected by storing it on another computer and only remotely, then the iteration count is not required at all.
@advanced_1248_h3
@advanced_1249_h3
File Encryption
File Encryption
@advanced_1249_p
@advanced_1250_p
The database files can be encrypted using two different algorithms: AES-128 and XTEA (using 32 rounds). The reasons for supporting XTEA is performance (XTEA is about twice as fast as AES) and to have an alternative algorithm if AES is suddenly broken.
The database files can be encrypted using two different algorithms: AES-128 and XTEA (using 32 rounds). The reasons for supporting XTEA is performance (XTEA is about twice as fast as AES) and to have an alternative algorithm if AES is suddenly broken.
@advanced_1250_p
@advanced_1251_p
When a user tries to connect to an encrypted database, the combination of the word 'file', @, and the file password is hashed using SHA-256. This hash value is transmitted to the server.
When a user tries to connect to an encrypted database, the combination of the word 'file', @, and the file password is hashed using SHA-256. This hash value is transmitted to the server.
@advanced_1251_p
@advanced_1252_p
When a new database file is created, a new cryptographically secure random salt value is generated. The size of the salt is 64 bit. The combination of the file password hash and the salt value is hashed 1024 times using SHA-256. The reason for the iteration is to make it harder for an attacker to calculate hash values for common passwords.
When a new database file is created, a new cryptographically secure random salt value is generated. The size of the salt is 64 bit. The combination of the file password hash and the salt value is hashed 1024 times using SHA-256. The reason for the iteration is to make it harder for an attacker to calculate hash values for common passwords.
@advanced_1252_p
@advanced_1253_p
The resulting hash value is used as the key for the block cipher algorithm (AES-128 or XTEA with 32 rounds). Then, an initialization vector (IV) key is calculated by hashing the key again using SHA-256. This is to make sure the IV is unknown to the attacker. The reason for using a secret IV is to protect against watermark attacks.
The resulting hash value is used as the key for the block cipher algorithm (AES-128 or XTEA with 32 rounds). Then, an initialization vector (IV) key is calculated by hashing the key again using SHA-256. This is to make sure the IV is unknown to the attacker. The reason for using a secret IV is to protect against watermark attacks.
@advanced_1253_p
@advanced_1254_p
Before saving a block of data (each block is 8 bytes long), the following operations are executed: First, the IV is calculated by encrypting the block number with the IV key (using the same block cipher algorithm). This IV is combined with the plain text using XOR. The resulting data is encrypted using the AES-128 or XTEA algorithm.
Before saving a block of data (each block is 8 bytes long), the following operations are executed: First, the IV is calculated by encrypting the block number with the IV key (using the same block cipher algorithm). This IV is combined with the plain text using XOR. The resulting data is encrypted using the AES-128 or XTEA algorithm.
@advanced_1254_p
@advanced_1255_p
When decrypting, the operation is done in reverse. First, the block is decrypted using the key, and then the IV is calculated combined with the decrypted text using XOR.
When decrypting, the operation is done in reverse. First, the block is decrypted using the key, and then the IV is calculated combined with the decrypted text using XOR.
@advanced_1255_p
@advanced_1256_p
Therefore, the block cipher mode of operation is CBC (Cipher-block chaining), but each chain is only one block long. The advantage over the ECB (Electronic codebook) mode is that patterns in the data are not revealed, and the advantage over multi block CBC is that flipped cipher text bits are not propagated to flipped plaintext bits in the next block.
Therefore, the block cipher mode of operation is CBC (Cipher-block chaining), but each chain is only one block long. The advantage over the ECB (Electronic codebook) mode is that patterns in the data are not revealed, and the advantage over multi block CBC is that flipped cipher text bits are not propagated to flipped plaintext bits in the next block.
@advanced_1256_p
@advanced_1257_p
Database encryption is meant for securing the database while it is not in use (stolen laptop and so on). It is not meant for cases where the attacker has access to files while the database is in use. When he has write access, he can for example replace pieces of files with pieces of older versions and manipulate data like this.
Database encryption is meant for securing the database while it is not in use (stolen laptop and so on). It is not meant for cases where the attacker has access to files while the database is in use. When he has write access, he can for example replace pieces of files with pieces of older versions and manipulate data like this.
@advanced_1257_p
@advanced_1258_p
File encryption slows down the performance of the database engine. Compared to unencrypted mode, database operations take about 2.2 times longer when using XTEA, and 2.5 times longer using AES (embedded mode).
File encryption slows down the performance of the database engine. Compared to unencrypted mode, database operations take about 2.2 times longer when using XTEA, and 2.5 times longer using AES (embedded mode).
@advanced_1258_h3
@advanced_1259_h3
Wrong Password Delay
Wrong Password Delay
@advanced_1259_p
@advanced_1260_p
To protect against remote brute force password attacks, the delay after each unsuccessful login gets double as long. Use the system properties h2.delayWrongPasswordMin and h2.delayWrongPasswordMax to change the minimum (the default is 250 milliseconds) or maximum delay (the default is 4000 milliseconds, or 4 seconds). The delay only applies for those using the wrong password. Normally there is no delay for a user that knows the correct password, with one exception: after using the wrong password, there is a delay of up (randomly distributed) the same delay as for a wrong password. This is to protect against parallel brute force attacks, so that an attacker needs to wait for the whole delay. Delays are synchronized. This is also required to protect against parallel attacks.
To protect against remote brute force password attacks, the delay after each unsuccessful login gets double as long. Use the system properties h2.delayWrongPasswordMin and h2.delayWrongPasswordMax to change the minimum (the default is 250 milliseconds) or maximum delay (the default is 4000 milliseconds, or 4 seconds). The delay only applies for those using the wrong password. Normally there is no delay for a user that knows the correct password, with one exception: after using the wrong password, there is a delay of up (randomly distributed) the same delay as for a wrong password. This is to protect against parallel brute force attacks, so that an attacker needs to wait for the whole delay. Delays are synchronized. This is also required to protect against parallel attacks.
@advanced_1260_h3
@advanced_1261_h3
SSL/TLS Connections
SSL/TLS Connections
@advanced_1261_p
@advanced_1262_p
Remote SSL/TLS connections are supported using the Java Secure Socket Extension (SSLServerSocket / SSLSocket). By default, anonymous SSL is enabled. The default cipher suite is <code>SSL_DH_anon_WITH_RC4_128_MD5</code> .
Remote SSL/TLS connections are supported using the Java Secure Socket Extension (SSLServerSocket / SSLSocket). By default, anonymous SSL is enabled. The default cipher suite is <code>SSL_DH_anon_WITH_RC4_128_MD5</code> .
@advanced_1262_p
@advanced_1263_p
To use your own keystore, set the system properties <code>javax.net.ssl.keyStore</code> and <code>javax.net.ssl.keyStorePassword</code> before starting the H2 server and client. See also <a href="http://java.sun.com/javase/6/docs/technotes/guides/security/jsse/JSSERefGuide.html#CustomizingStores">Customizing the Default Key and Trust Stores, Store Types, and Store Passwords</a> for more information.
To use your own keystore, set the system properties <code>javax.net.ssl.keyStore</code> and <code>javax.net.ssl.keyStorePassword</code> before starting the H2 server and client. See also <a href="http://java.sun.com/javase/6/docs/technotes/guides/security/jsse/JSSERefGuide.html#CustomizingStores">Customizing the Default Key and Trust Stores, Store Types, and Store Passwords</a> for more information.
@advanced_1263_p
@advanced_1264_p
To disable anonymous SSL, set the system property <code>h2.enableAnonymousSSL</code> to false.
To disable anonymous SSL, set the system property <code>h2.enableAnonymousSSL</code> to false.
@advanced_1264_h3
@advanced_1265_h3
HTTPS Connections
HTTPS Connections
@advanced_1265_p
@advanced_1266_p
The web server supports HTTP and HTTPS connections using SSLServerSocket. There is a default self-certified certificate to support an easy starting point, but custom certificates are supported as well.
The web server supports HTTP and HTTPS connections using SSLServerSocket. There is a default self-certified certificate to support an easy starting point, but custom certificates are supported as well.
@advanced_1266_h2
@advanced_1267_h2
Universally Unique Identifiers (UUID)
Universally Unique Identifiers (UUID)
@advanced_1267_p
@advanced_1268_p
This database supports the UUIDs. Also supported is a function to create new UUIDs using a cryptographically strong pseudo random number generator. With random UUIDs, the chance of two having the same value can be calculated using the probability theory. See also 'Birthday Paradox'. Standardized randomly generated UUIDs have 122 random bits. 4 bits are used for the version (Randomly generated UUID), and 2 bits for the variant (Leach-Salz). This database supports generating such UUIDs using the built-in function RANDOM_UUID(). Here is a small program to estimate the probability of having two identical UUIDs after generating a number of values:
This database supports the UUIDs. Also supported is a function to create new UUIDs using a cryptographically strong pseudo random number generator. With random UUIDs, the chance of two having the same value can be calculated using the probability theory. See also 'Birthday Paradox'. Standardized randomly generated UUIDs have 122 random bits. 4 bits are used for the version (Randomly generated UUID), and 2 bits for the variant (Leach-Salz). This database supports generating such UUIDs using the built-in function RANDOM_UUID(). Here is a small program to estimate the probability of having two identical UUIDs after generating a number of values:
@advanced_1268_p
@advanced_1269_p
Some values are:
Some values are:
@advanced_1269_p
@advanced_1270_p
To help non-mathematicians understand what those numbers mean, here a comparison: One's annual risk of being hit by a meteorite is estimated to be one chance in 17 billion, that means the probability is about 0.000'000'000'06.
To help non-mathematicians understand what those numbers mean, here a comparison: One's annual risk of being hit by a meteorite is estimated to be one chance in 17 billion, that means the probability is about 0.000'000'000'06.
@advanced_1270_h2
@advanced_1271_h2
Settings Read from System Properties
Settings Read from System Properties
@advanced_1271_p
@advanced_1272_p
Some settings of the database can be set on the command line using -DpropertyName=value. It is usually not required to change those settings manually. The settings are case sensitive. Example:
Some settings of the database can be set on the command line using -DpropertyName=value. It is usually not required to change those settings manually. The settings are case sensitive. Example:
@advanced_1272_p
@advanced_1273_p
The current value of the settings can be read in the table INFORMATION_SCHEMA.SETTINGS.
The current value of the settings can be read in the table INFORMATION_SCHEMA.SETTINGS.
@advanced_1273_p
@advanced_1274_p
For a complete list of settings, see <a href="../javadoc/org/h2/constant/SysProperties.html">SysProperties</a> .
For a complete list of settings, see <a href="../javadoc/org/h2/constant/SysProperties.html">SysProperties</a> .
@advanced_1274_h2
@advanced_1275_h2
Setting the Server Bind Address
Setting the Server Bind Address
@advanced_1275_p
@advanced_1276_p
Usually server sockets accept connections on any/all local addresses. This may be a problem on multi-homed hosts. To bind only to one address, use the system property h2.bindAddress. This setting is used for both regular server sockets and for SSL server sockets. IPv4 and IPv6 address formats are supported.
Usually server sockets accept connections on any/all local addresses. This may be a problem on multi-homed hosts. To bind only to one address, use the system property h2.bindAddress. This setting is used for both regular server sockets and for SSL server sockets. IPv4 and IPv6 address formats are supported.
@advanced_1276_h2
@advanced_1277_h2
Limitations
@advanced_1278_p
This database has the following known limitations:
@advanced_1279_li
The maximum file size is currently 256 GB for the data, and 256 GB for the index. This number is excluding BLOB and CLOB data: Every CLOB or BLOB can be up to 256 GB as well.
@advanced_1280_li
The maximum file size for FAT or FAT32 file systems is 4 GB. That means when using FAT or FAT32, the limit is 4 GB for the data. This is the limitation of the file system, and this database does not provide a workaround for this problem. The suggested solution is to use another file system.
@advanced_1281_li
There is a limit on the complexity of SQL statements. Statements of the following form will result in a stack overflow exception:
@advanced_1282_li
There is no limit for the following entities, except the memory and storage capacity: maximum identifier length, maximum number of tables, maximum number of columns, maximum number of indexes, maximum number of parameters, maximum number of triggers, and maximum number of other database objects.
@advanced_1283_li
For limitations on data types, see the documentation of the respective Java data type or the data type documentation of this database.
@advanced_1284_h2
Glossary and Links
Glossary and Links
@advanced_1277_th
@advanced_1285_th
Term
Term
@advanced_1278_th
@advanced_1286_th
Description
Description
@advanced_1279_td
@advanced_1287_td
AES-128
AES-128
@advanced_1280_td
@advanced_1288_td
A block encryption algorithm. See also: <a href="http://en.wikipedia.org/wiki/Advanced_Encryption_Standard">Wikipedia: AES</a>
A block encryption algorithm. See also: <a href="http://en.wikipedia.org/wiki/Advanced_Encryption_Standard">Wikipedia: AES</a>
@advanced_1281_td
@advanced_1289_td
Birthday Paradox
Birthday Paradox
@advanced_1282_td
@advanced_1290_td
Describes the higher than expected probability that two persons in a room have the same birthday. Also valid for randomly generated UUIDs. See also: <a href="http://en.wikipedia.org/wiki/Birthday_paradox">Wikipedia: Birthday Paradox</a>
Describes the higher than expected probability that two persons in a room have the same birthday. Also valid for randomly generated UUIDs. See also: <a href="http://en.wikipedia.org/wiki/Birthday_paradox">Wikipedia: Birthday Paradox</a>
@advanced_1283_td
@advanced_1291_td
Digest
Digest
@advanced_1284_td
@advanced_1292_td
Protocol to protect a password (but not to protect data). See also: <a href="http://www.faqs.org/rfcs/rfc2617.html">RFC 2617: HTTP Digest Access Authentication</a>
Protocol to protect a password (but not to protect data). See also: <a href="http://www.faqs.org/rfcs/rfc2617.html">RFC 2617: HTTP Digest Access Authentication</a>
@advanced_1285_td
@advanced_1293_td
GCJ
GCJ
@advanced_1286_td
@advanced_1294_td
GNU Compiler for Java. <a href="http://gcc.gnu.org/java/">http://gcc.gnu.org/java/</a> and <a href="http://nativej.mtsystems.ch">http://nativej.mtsystems.ch/ (not free any more)</a>
GNU Compiler for Java. <a href="http://gcc.gnu.org/java/">http://gcc.gnu.org/java/</a> and <a href="http://nativej.mtsystems.ch">http://nativej.mtsystems.ch/ (not free any more)</a>
@advanced_1287_td
@advanced_1295_td
HTTPS
HTTPS
@advanced_1288_td
@advanced_1296_td
A protocol to provide security to HTTP connections. See also: <a href="http://www.ietf.org/rfc/rfc2818.txt">RFC 2818: HTTP Over TLS</a>
A protocol to provide security to HTTP connections. See also: <a href="http://www.ietf.org/rfc/rfc2818.txt">RFC 2818: HTTP Over TLS</a>
@advanced_1289_td
@advanced_1297_td
Modes of Operation
Modes of Operation
@advanced_1290_a
@advanced_1298_a
Wikipedia: Block cipher modes of operation
Wikipedia: Block cipher modes of operation
@advanced_1291_td
@advanced_1299_td
Salt
Salt
@advanced_1292_td
@advanced_1300_td
Random number to increase the security of passwords. See also: <a href="http://en.wikipedia.org/wiki/Key_derivation_function">Wikipedia: Key derivation function</a>
Random number to increase the security of passwords. See also: <a href="http://en.wikipedia.org/wiki/Key_derivation_function">Wikipedia: Key derivation function</a>
@advanced_1293_td
@advanced_1301_td
SHA-256
SHA-256
@advanced_1294_td
@advanced_1302_td
A cryptographic one-way hash function. See also: <a href="http://en.wikipedia.org/wiki/SHA_family">Wikipedia: SHA hash functions</a>
A cryptographic one-way hash function. See also: <a href="http://en.wikipedia.org/wiki/SHA_family">Wikipedia: SHA hash functions</a>
@advanced_1295_td
@advanced_1303_td
SQL Injection
SQL Injection
@advanced_1296_td
@advanced_1304_td
A security vulnerability where an application generates SQL statements with embedded user input. See also: <a href="http://en.wikipedia.org/wiki/SQL_injection">Wikipedia: SQL Injection</a>
A security vulnerability where an application generates SQL statements with embedded user input. See also: <a href="http://en.wikipedia.org/wiki/SQL_injection">Wikipedia: SQL Injection</a>
@advanced_1297_td
@advanced_1305_td
Watermark Attack
Watermark Attack
@advanced_1298_td
@advanced_1306_td
Security problem of certain encryption programs where the existence of certain data can be proven without decrypting. For more information, search in the internet for 'watermark attack cryptoloop'
Security problem of certain encryption programs where the existence of certain data can be proven without decrypting. For more information, search in the internet for 'watermark attack cryptoloop'
@advanced_1299_td
@advanced_1307_td
SSL/TLS
SSL/TLS
@advanced_1300_td
@advanced_1308_td
Secure Sockets Layer / Transport Layer Security. See also: <a href="http://java.sun.com/products/jsse/">Java Secure Socket Extension (JSSE)</a>
Secure Sockets Layer / Transport Layer Security. See also: <a href="http://java.sun.com/products/jsse/">Java Secure Socket Extension (JSSE)</a>
@advanced_1301_td
@advanced_1309_td
XTEA
XTEA
@advanced_1302_td
@advanced_1310_td
A block encryption algorithm. See also: <a href="http://en.wikipedia.org/wiki/XTEA">Wikipedia: XTEA</a>
A block encryption algorithm. See also: <a href="http://en.wikipedia.org/wiki/XTEA">Wikipedia: XTEA</a>
@build_1000_h1
@build_1000_h1
...
@@ -1019,7 +1043,7 @@ Change Log
...
@@ -1019,7 +1043,7 @@ Change Log
Next Version (unreleased)
Next Version (unreleased)
@changelog_1002_li
@changelog_1002_li
-
User defined functions can now be overloaded. The Java class can contain multiple classes with the same name that only differ in the number of parameters. Thanks to Gary Tong for providing a patch!
@changelog_1003_h2
@changelog_1003_h2
Version 1.0.73 (2008-05-31)
Version 1.0.73 (2008-05-31)
...
@@ -3761,70 +3785,70 @@ H2 (for 'Hypersonic 2') is free a Java SQL DBMS. Clustering, embedded and server
...
@@ -3761,70 +3785,70 @@ H2 (for 'Hypersonic 2') is free a Java SQL DBMS. Clustering, embedded and server
History and Roadmap
History and Roadmap
@history_1001_a
@history_1001_a
History of this Database Engine
Change Log
@history_1002_a
@history_1002_a
Why Java
Roadmap
@history_1003_a
@history_1003_a
Change Log
History of this Database Engine
@history_1004_a
@history_1004_a
Roadmap
Why Java
@history_1005_a
@history_1005_a
Supporters
Supporters
@history_1006_h2
@history_1006_h2
History of this Database Engine
Change Log
@history_1007_p
@history_1007_p
The development of H2 was started in May 2004, but it was first published on December 14th 2005. The author of H2, Thomas Mueller, is also the original developer of Hypersonic SQL. In 2001, he joined PointBase Inc. where he created PointBase Micro. At that point, he had to discontinue Hypersonic SQL, but then the HSQLDB Group was formed to continued to work on the Hypersonic SQL codebase. The name H2 stands for Hypersonic 2; however H2 does not share any code with Hypersonic SQL or HSQLDB. H2 is built from scratch.
The up-to-date change log is available at <a href="http://www.h2database.com/html/changelog.html">http://www.h2database.com/html/changelog.html</a>
@history_1008_h2
@history_1008_h2
Why Java
Roadmap
@history_1009_p
@history_1009_p
The current roadmap is available at <a href="http://www.h2database.com/html/roadmap.html">http://www.h2database.com/html/roadmap.html</a>
@history_1010_h2
History of this Database Engine
@history_1011_p
The development of H2 was started in May 2004, but it was first published on December 14th 2005. The author of H2, Thomas Mueller, is also the original developer of Hypersonic SQL. In 2001, he joined PointBase Inc. where he created PointBase Micro. At that point, he had to discontinue Hypersonic SQL, but then the HSQLDB Group was formed to continued to work on the Hypersonic SQL codebase. The name H2 stands for Hypersonic 2; however H2 does not share any code with Hypersonic SQL or HSQLDB. H2 is built from scratch.
@history_1012_h2
Why Java
@history_1013_p
A few reasons using a Java database are:
A few reasons using a Java database are:
@history_1010_li
@history_1014_li
Very simple to integrate in Java applications
Very simple to integrate in Java applications
@history_1011_li
@history_1015_li
Support for many different platforms
Support for many different platforms
@history_1012_li
@history_1016_li
More secure than native applications (no buffer overflows)
More secure than native applications (no buffer overflows)
@history_1013_li
@history_1017_li
User defined functions (or triggers) run very fast
User defined functions (or triggers) run very fast
@history_1014_li
@history_1018_li
Unicode support
Unicode support
@history_1015_p
@history_1019_p
Some people think that Java is still too slow for low level operations, but this is not the case (not any more). In general, the code can be written a lot faster than using C or C++. Like that, it is possible to concentrate on improving the algorithms (that make the application faster) rather than porting the code and dealing with low level stuff (such as memory management or dealing with threads). Garbage collection is now probably faster than manual memory management.
Some people think that Java is still too slow for low level operations, but this is not the case (not any more). In general, the code can be written a lot faster than using C or C++. Like that, it is possible to concentrate on improving the algorithms (that make the application faster) rather than porting the code and dealing with low level stuff (such as memory management or dealing with threads). Garbage collection is now probably faster than manual memory management.
@history_1016_p
@history_1020_p
A lot of features are already built in (for example Unicode, network libraries). It is very easy to write secure code because buffer overflows can not occur. Some features such as the reflection mechanism can be used for randomized testing.
A lot of features are already built in (for example Unicode, network libraries). It is very easy to write secure code because buffer overflows can not occur. Some features such as the reflection mechanism can be used for randomized testing.
@history_1017_p
@history_1021_p
Java is also future proof: A lot of companies support Java, and it is now open source.
Java is also future proof: A lot of companies support Java, and it is now open source.
@history_1018_p
This software does not rely on many Java libraries or other software, to increase the portability and ease of use, and for performance reasons. For example, the encryption algorithms and many library functions are implemented in the database instead of using the existing libraries. Libraries that are not available in open source Java implementations (such as Swing) are not used or only used for specific features.
@history_1019_h2
Change Log
@history_1020_p
The up-to-date change log is available here: <a href="http://www.h2database.com/html/changelog.html">http://www.h2database.com/html/changelog.html</a>
@history_1021_h2
Roadmap
@history_1022_p
@history_1022_p
The current roadmap is available here: <a href="http://www.h2database.com/html/roadmap.html">http://www.h2database.com/html/roadmap.html</a>
This software does not rely on many Java libraries or other software, to increase the portability and ease of use, and for performance reasons. For example, the encryption algorithms and many library functions are implemented in the database instead of using the existing libraries. Libraries that are not available in open source Java implementations (such as Swing) are not used or only used for specific features.
アプリケーションから結果が返される前に、全ての行はデータベースによって読み取られます。 サーバー側のカーソルは現在サポートされていません。もし最初の数行がアプリケーションに読み取られたら、 result setサイズはパフォーマンスを改善するために制限されます。これは、クエリーの LIMIT を使用することで 実現できます (例: SELECT * FROM TEST LIMIT 100)、または Statement.setMaxRows(max) を使用します。
アプリケーションから結果が返される前に、全ての行はデータベースによって読み取られます。 サーバー側のカーソルは現在サポートされていません。もし最初の数行がアプリケーションに読み取られたら、 result setサイズはパフォーマンスを改善するために制限されます。これは、クエリーの LIMIT を使用することで 実現できます (例: SELECT * FROM TEST LIMIT 100)、または Statement.setMaxRows(max) を使用します。
@advanced_1027_h3
@advanced_1028_h3
大きなResult Set と外部ソート
大きなResult Set と外部ソート
@advanced_1028_p
@advanced_1029_p
1000行以上のresult setのために、結果はディスクにバッファーされます。 もし ORDER BY が使用されていたら、ソートは、外部ソートアルゴリズムを使用して 完了しています。このケースでは、それぞれの行のブロックはクイックソートを使用してソートされ、 ディスクに書き込まれています; データを読み込んでいる時、ブロックは一緒にマージされます。
1000行以上のresult setのために、結果はディスクにバッファーされます。 もし ORDER BY が使用されていたら、ソートは、外部ソートアルゴリズムを使用して 完了しています。このケースでは、それぞれの行のブロックはクイックソートを使用してソートされ、 ディスクに書き込まれています; データを読み込んでいる時、ブロックは一緒にマージされます。
#The database allows multiple concurrent connections to the same database. To make sure all connections only see consistent data, table level locking is used by default. This mechanism does not allow high concurrency, but is very fast. Shared locks and exclusive locks are supported. Before reading from a table, the database tries to add a shared lock to the table (this is only possible if there is no exclusive lock on the object by another connection). If the shared lock is added successfully, the table can be read. It is allowed that other connections also have a shared lock on the same object. If a connection wants to write to a table (update or delete a row), an exclusive lock is required. To get the exclusive lock, other connection must not have any locks on the object. After the connection commits, all locks are released. This database keeps all locks in memory.
#The database allows multiple concurrent connections to the same database. To make sure all connections only see consistent data, table level locking is used by default. This mechanism does not allow high concurrency, but is very fast. Shared locks and exclusive locks are supported. Before reading from a table, the database tries to add a shared lock to the table (this is only possible if there is no exclusive lock on the object by another connection). If the shared lock is added successfully, the table can be read. It is allowed that other connections also have a shared lock on the same object. If a connection wants to write to a table (update or delete a row), an exclusive lock is required. To get the exclusive lock, other connection must not have any locks on the object. After the connection commits, all locks are released. This database keeps all locks in memory.
#The MVCC feature allows higher concurrency than using (table level or row level) locks. When using MVCC in this database, delete, insert and update operations will only issue a shared lock on the table. An exclusive lock is still used when adding or removing columns, when dropping the table, and when using SELECT ... FOR UPDATE. Connections only 'see' committed data, and own changes. That means, if connection A updates a row but doesn't commit this change yet, connection B will see the old value. Only when the change is committed, the new value is visible by other connections (read committed). If multiple connections concurrently try to update the same row, this database fails fast: a concurrent update exception is thrown.
#The MVCC feature allows higher concurrency than using (table level or row level) locks. When using MVCC in this database, delete, insert and update operations will only issue a shared lock on the table. An exclusive lock is still used when adding or removing columns, when dropping the table, and when using SELECT ... FOR UPDATE. Connections only 'see' committed data, and own changes. That means, if connection A updates a row but doesn't commit this change yet, connection B will see the old value. Only when the change is committed, the new value is visible by other connections (read committed). If multiple connections concurrently try to update the same row, this database fails fast: a concurrent update exception is thrown.
@advanced_1065_p
@advanced_1066_p
#To use the MVCC feature, append MVCC=TRUE to the database URL:
#To use the MVCC feature, append MVCC=TRUE to the database URL:
#This database tries to be as much standard compliant as possible. For the SQL language, ANSI/ISO is the main standard. There are several versions that refer to the release date: SQL-92, SQL:1999, and SQL:2003. Unfortunately, the standard documentation is not freely available. Another problem is that important features are not standardized. Whenever this is the case, this database tries to be compatible to other databases.
#This database tries to be as much standard compliant as possible. For the SQL language, ANSI/ISO is the main standard. There are several versions that refer to the release date: SQL-92, SQL:1999, and SQL:2003. Unfortunately, the standard documentation is not freely available. Another problem is that important features are not standardized. Whenever this is the case, this database tries to be compatible to other databases.
@advanced_1106_h2
@advanced_1107_h2
Windowsサービスとして実行する
Windowsサービスとして実行する
@advanced_1107_p
@advanced_1108_p
ネイティブラッパー / アダプタを使用して、JavaアプリケーションはWindowsサービスとして実行できます。これを実行するために、様々なツールが有効です。Tanuki Software, Inc. (<a href="http://wrapper.tanukisoftware.org/">http://wrapper.tanukisoftware.org/</a>) のJavaサービスラッパーはインストールが含まれています。H2データベースエンジンサービスのインストール、起動、終了とアンインストールのためのバッチファイルが添付されます。このサービスは、TCPサーバーとH2コンソールWebアプリケーションが含まれます。バッチファイルは、H2/service ディレクトリに配置されています。
ネイティブラッパー / アダプタを使用して、JavaアプリケーションはWindowsサービスとして実行できます。これを実行するために、様々なツールが有効です。Tanuki Software, Inc. (<a href="http://wrapper.tanukisoftware.org/">http://wrapper.tanukisoftware.org/</a>) のJavaサービスラッパーはインストールが含まれています。H2データベースエンジンサービスのインストール、起動、終了とアンインストールのためのバッチファイルが添付されます。このサービスは、TCPサーバーとH2コンソールWebアプリケーションが含まれます。バッチファイルは、H2/service ディレクトリに配置されています。
#PostgreSQL ODBC Driver Setup requires a database password; that means it is not possible to connect to H2 databases without password. This is a limitation of the ODBC driver.
#PostgreSQL ODBC Driver Setup requires a database password; that means it is not possible to connect to H2 databases without password. This is a limitation of the ODBC driver.
#The database can be used from Microsoft .NET even without using Java, by using IKVM.NET. You can access a H2 database on .NET using the JDBC API, or using the ADO.NET interface.
#The database can be used from Microsoft .NET even without using Java, by using IKVM.NET. You can access a H2 database on .NET using the JDBC API, or using the ADO.NET interface.
@advanced_1167_h3
@advanced_1168_h3
#Using the ADO.NET API on .NET
#Using the ADO.NET API on .NET
@advanced_1168_p
@advanced_1169_p
#An implementation of the ADO.NET interface is available in the open source project <a href="http://code.google.com/p/h2sharp">H2Sharp</a> .
#An implementation of the ADO.NET interface is available in the open source project <a href="http://code.google.com/p/h2sharp">H2Sharp</a> .
@advanced_1169_h3
@advanced_1170_h3
#Using the JDBC API on .NET
#Using the JDBC API on .NET
@advanced_1170_li
@advanced_1171_li
#Install the .NET Framework from <a href="http://www.microsoft.com">Microsoft</a> . Mono has not yet been tested.
#Install the .NET Framework from <a href="http://www.microsoft.com">Microsoft</a> . Mono has not yet been tested.
#By default, MySQL calls fsync for each commit. When using one of those methods, only around 60 write operations per second can be achieved, which is consistent with the RPM rate of the hard drive used. Unfortunately, even when calling FileDescriptor.sync() or FileChannel.force(), data is not always persisted to the hard drive, because most hard drives do not obey fsync(): see <a href="http://hardware.slashdot.org/article.pl?sid=05/05/13/0529252">Your Hard Drive Lies to You</a> . In Mac OS X, fsync does not flush hard drive buffers. See <a href="http://lists.apple.com/archives/darwin-dev/2005/Feb/msg00072.html">Bad fsync?</a> . So the situation is confusing, and tests prove there is a problem.
#By default, MySQL calls fsync for each commit. When using one of those methods, only around 60 write operations per second can be achieved, which is consistent with the RPM rate of the hard drive used. Unfortunately, even when calling FileDescriptor.sync() or FileChannel.force(), data is not always persisted to the hard drive, because most hard drives do not obey fsync(): see <a href="http://hardware.slashdot.org/article.pl?sid=05/05/13/0529252">Your Hard Drive Lies to You</a> . In Mac OS X, fsync does not flush hard drive buffers. See <a href="http://lists.apple.com/archives/darwin-dev/2005/Feb/msg00072.html">Bad fsync?</a> . So the situation is confusing, and tests prove there is a problem.
#Afterwards, SQL statements with text and number literals are not allowed any more. That means, SQL statement of the form WHERE NAME='abc' or WHERE CustomerId=10 will fail. It is still possible to use PreparedStatements and parameters as described above. Also, it is still possible to generate SQL statements dynamically, and use the Statement API, as long as the SQL statements do not include literals. There is also a second mode where number literals are allowed: SET ALLOW_LITERALS NUMBERS. To allow all literals, execute SET ALLOW_LITERALS ALL (this is the default setting). Literals can only be enabled or disabled by an administrator.
#Afterwards, SQL statements with text and number literals are not allowed any more. That means, SQL statement of the form WHERE NAME='abc' or WHERE CustomerId=10 will fail. It is still possible to use PreparedStatements and parameters as described above. Also, it is still possible to generate SQL statements dynamically, and use the Statement API, as long as the SQL statements do not include literals. There is also a second mode where number literals are allowed: SET ALLOW_LITERALS NUMBERS. To allow all literals, execute SET ALLOW_LITERALS ALL (this is the default setting). Literals can only be enabled or disabled by an administrator.
#By default there is no restriction on loading classes and executing Java code for admins. That means an admin may call system functions such as System.setProperty by executing:
#By default there is no restriction on loading classes and executing Java code for admins. That means an admin may call system functions such as System.setProperty by executing:
@advanced_1240_p
@advanced_1241_p
#To restrict users (including admins) from loading classes and executing code, the list of allowed classes can be set in the system property h2.allowedClasses in the form of a comma separated list of classes or patterns (items ending with '*'). By default all classes are allowed. Example:
#To restrict users (including admins) from loading classes and executing code, the list of allowed classes can be set in the system property h2.allowedClasses in the form of a comma separated list of classes or patterns (items ending with '*'). By default all classes are allowed. Example:
@advanced_1241_p
@advanced_1242_p
#This mechanism is used for all user classes, including database event listeners, trigger classes, user-defined functions, user-defined aggregate functions, and JDBC driver classes (with the exception of the H2 driver) when using the H2 Console.
#This mechanism is used for all user classes, including database event listeners, trigger classes, user-defined functions, user-defined aggregate functions, and JDBC driver classes (with the exception of the H2 driver) when using the H2 Console.
#To protect against remote brute force password attacks, the delay after each unsuccessful login gets double as long. Use the system properties h2.delayWrongPasswordMin and h2.delayWrongPasswordMax to change the minimum (the default is 250 milliseconds) or maximum delay (the default is 4000 milliseconds, or 4 seconds). The delay only applies for those using the wrong password. Normally there is no delay for a user that knows the correct password, with one exception: after using the wrong password, there is a delay of up (randomly distributed) the same delay as for a wrong password. This is to protect against parallel brute force attacks, so that an attacker needs to wait for the whole delay. Delays are synchronized. This is also required to protect against parallel attacks.
#To protect against remote brute force password attacks, the delay after each unsuccessful login gets double as long. Use the system properties h2.delayWrongPasswordMin and h2.delayWrongPasswordMax to change the minimum (the default is 250 milliseconds) or maximum delay (the default is 4000 milliseconds, or 4 seconds). The delay only applies for those using the wrong password. Normally there is no delay for a user that knows the correct password, with one exception: after using the wrong password, there is a delay of up (randomly distributed) the same delay as for a wrong password. This is to protect against parallel brute force attacks, so that an attacker needs to wait for the whole delay. Delays are synchronized. This is also required to protect against parallel attacks.
#To use your own keystore, set the system properties <code>javax.net.ssl.keyStore</code> and <code>javax.net.ssl.keyStorePassword</code> before starting the H2 server and client. See also <a href="http://java.sun.com/javase/6/docs/technotes/guides/security/jsse/JSSERefGuide.html#CustomizingStores">Customizing the Default Key and Trust Stores, Store Types, and Store Passwords</a> for more information.
#To use your own keystore, set the system properties <code>javax.net.ssl.keyStore</code> and <code>javax.net.ssl.keyStorePassword</code> before starting the H2 server and client. See also <a href="http://java.sun.com/javase/6/docs/technotes/guides/security/jsse/JSSERefGuide.html#CustomizingStores">Customizing the Default Key and Trust Stores, Store Types, and Store Passwords</a> for more information.
@advanced_1263_p
@advanced_1264_p
#To disable anonymous SSL, set the system property <code>h2.enableAnonymousSSL</code> to false.
#To disable anonymous SSL, set the system property <code>h2.enableAnonymousSSL</code> to false.
#The current value of the settings can be read in the table INFORMATION_SCHEMA.SETTINGS.
#The current value of the settings can be read in the table INFORMATION_SCHEMA.SETTINGS.
@advanced_1273_p
@advanced_1274_p
#For a complete list of settings, see <a href="../javadoc/org/h2/constant/SysProperties.html">SysProperties</a> .
#For a complete list of settings, see <a href="../javadoc/org/h2/constant/SysProperties.html">SysProperties</a> .
@advanced_1274_h2
@advanced_1275_h2
#Setting the Server Bind Address
#Setting the Server Bind Address
@advanced_1275_p
@advanced_1276_p
#Usually server sockets accept connections on any/all local addresses. This may be a problem on multi-homed hosts. To bind only to one address, use the system property h2.bindAddress. This setting is used for both regular server sockets and for SSL server sockets. IPv4 and IPv6 address formats are supported.
#Usually server sockets accept connections on any/all local addresses. This may be a problem on multi-homed hosts. To bind only to one address, use the system property h2.bindAddress. This setting is used for both regular server sockets and for SSL server sockets. IPv4 and IPv6 address formats are supported.
@advanced_1276_h2
@advanced_1277_h2
#Limitations
@advanced_1278_p
#This database has the following known limitations:
@advanced_1279_li
#The maximum file size is currently 256 GB for the data, and 256 GB for the index. This number is excluding BLOB and CLOB data: Every CLOB or BLOB can be up to 256 GB as well.
@advanced_1280_li
#The maximum file size for FAT or FAT32 file systems is 4 GB. That means when using FAT or FAT32, the limit is 4 GB for the data. This is the limitation of the file system, and this database does not provide a workaround for this problem. The suggested solution is to use another file system.
@advanced_1281_li
#There is a limit on the complexity of SQL statements. Statements of the following form will result in a stack overflow exception:
@advanced_1282_li
#There is no limit for the following entities, except the memory and storage capacity: maximum identifier length, maximum number of tables, maximum number of columns, maximum number of indexes, maximum number of parameters, maximum number of triggers, and maximum number of other database objects.
@advanced_1283_li
#For limitations on data types, see the documentation of the respective Java data type or the data type documentation of this database.
JavaのGNUコンパイラー<a href="http://gcc.gnu.org/java/">http://gcc.gnu.org/java/</a> and <a href="http://nativej.mtsystems.ch">http://nativej.mtsystems.ch/ (not free any more)</a>
JavaのGNUコンパイラー<a href="http://gcc.gnu.org/java/">http://gcc.gnu.org/java/</a> and <a href="http://nativej.mtsystems.ch">http://nativej.mtsystems.ch/ (not free any more)</a>
@advanced_1287_td
@advanced_1295_td
HTTPS
HTTPS
@advanced_1288_td
@advanced_1296_td
セキュリティをHTTP接続に提供するプロトコル。こちらもご覧下さい: <a href="http://www.ietf.org/rfc/rfc2818.txt">RFC 2818: HTTP Over TLS</a>
セキュリティをHTTP接続に提供するプロトコル。こちらもご覧下さい: <a href="http://www.ietf.org/rfc/rfc2818.txt">RFC 2818: HTTP Over TLS</a>
#User defined functions can now be overloaded. The Java class can contain multiple classes with the same name that only differ in the number of parameters. Thanks to Gary Tong for providing a patch!
@changelog_1003_h2
@changelog_1003_h2
#Version 1.0.73 (2008-05-31)
#Version 1.0.73 (2008-05-31)
...
@@ -3763,70 +3787,70 @@ H2 (for 'Hypersonic 2') is free a Java SQL DBMS. Clustering, embedded and server
...
@@ -3763,70 +3787,70 @@ H2 (for 'Hypersonic 2') is free a Java SQL DBMS. Clustering, embedded and server
#A lot of features are already built in (for example Unicode, network libraries). It is very easy to write secure code because buffer overflows can not occur. Some features such as the reflection mechanism can be used for randomized testing.
#A lot of features are already built in (for example Unicode, network libraries). It is very easy to write secure code because buffer overflows can not occur. Some features such as the reflection mechanism can be used for randomized testing.
#The up-to-date change log is available here: <a href="http://www.h2database.com/html/changelog.html">http://www.h2database.com/html/changelog.html</a>
@history_1021_h2
ロードマップ
@history_1022_p
@history_1022_p
#The current roadmap is available here: <a href="http://www.h2database.com/html/roadmap.html">http://www.h2database.com/html/roadmap.html</a>
