Managing Cursors and JDBC Objects to Prevent ORA-01000

Understanding the Connection Between Cursors and JDBC

• ORA-01000 maximum-open-cursors error occurs when the database instance runs out of available cursors.
• Each JDBC ResultSet is supported by a single cursor on the database.
• Each JDBC Connection can handle multiple transactions, but only one transaction at a time.

Configuration and Management

• Open cursor limit is configured on the database instance.
• Maximum cursors can be increased to accommodate higher demand.
• Pending transactions can be managed by increasing the number of connections.

Identifying and Fixing Leaks

• Cursor leaks occur when ResultSet objects are not closed, releasing their associated database cursors.
• To prevent leaks, ensure that ResultSet objects are always closed within a finally block.

Best Practices for JDBC Object Handling

• Hold JDBC objects safely in instance or class members if they will be reused.
• Use local variables for ResultSets, as they are typically used and closed within a single function.
• In a multi-threaded environment, store JDBC objects in a thread-safe manner or use connection pooling.

Debugging Techniques

• Static code analysis tools like Findbugs can detect potential leaks in development.
• Runtime logging can help pinpoint the source of the leak by tracking open and closed objects.
• Database monitoring tools can identify SQL statements that are causing excessive cursor usage, indicating a potential leak.

Other Considerations

• Setting the ResultSet holdability to CLOSE_CURSORS_OVER_COMMIT closes the ResultSet when the transaction is committed.
• Debugging JDBC drivers can provide insights into where close statements may be missing.
• Weak references for closing connections are generally not a reliable solution due to potential GC interference.