Use PageStore lock to access cache (issue #1371)

h2/src/main/org/h2/engine/Database.java

@@ -2077,7 +2077,7 @@ public class Database implements DataHandler {
         }
         cacheSize = kb;
         if (pageStore != null) {
-            pageStore.getCache().setMaxMemory(kb);
+            pageStore.setMaxMemory(kb);
         }
         if (store != null) {
             store.setCacheSize(Math.max(1, kb));

h2/src/main/org/h2/store/PageStore.java

@@ -2028,4 +2028,8 @@ public class PageStore implements CacheWriter {
         backupLevel += start ? 1 : -1;
     }
 
+    public synchronized void setMaxMemory(int size) {
+        cache.setMaxMemory(size);
+    }
+
 }