fix spelling

h2/src/docsrc/html/mvstore.html

@@ -468,7 +468,7 @@ This is work in progress. To try it out, append
 <code>;MV_STORE=TRUE</code>
 to the database URL. In general, performance should be
 similar than the current default storage engine (the page store).
-Even thought it can be used with the default table level locking,
+Even though it can be used with the default table level locking,
 it is recommended to use it together with the MVCC mode 
 (to do that, append <code>;MVCC=TRUE</code> to the database URL).
 </p>
@@ -498,7 +498,7 @@ The MVStore does not have a record size limit.
 <p>
 The code is still experimental at this stage.
 The API as well as the behavior may partially change.
-Features may be added and removed (even thought the main features will stay).
+Features may be added and removed (even though the main features will stay).
 </p>
 
 <h2 id="requirements">Requirements</h2>

h2/src/main/org/h2/mvstore/db/TransactionStore.java

@@ -1067,8 +1067,8 @@ public class TransactionStore {
                 // added or updated by this transaction
                 transaction.log(mapId, key, current);
                 if (!map.replace(key, current, newValue)) {
-                    // strange, somebody overwrite the value
-                    // even thought the change was not committed
+                    // strange, somebody overwrote the value
+                    // even though the change was not committed
                     transaction.logUndo();
                     return false;
                 }