ORA-609 is an Oracle error code that indicates a “listener process failure.” This error occurs when the database client (such as an application or another database) attempts to establish a connection to the Oracle Database, but the connection cannot be established due to a failure in the listener process.

Here’s what the ORA-609 error typically means and some potential causes:

1. Listener Process Failure: The error indicates that the listener process responsible for accepting incoming connections to the Oracle Database has encountered an issue or has stopped functioning properly.
2. Potential Causes:

• Listener Service Not Running: The Oracle listener service might not be running or might have crashed, preventing it from accepting new connections.
• Listener Configuration Issues: Incorrect configuration settings for the listener, such as incorrect port numbers, incorrect network addresses, or misconfigured listener.ora file, can cause connection failures.
• Network Connectivity Problems: Network issues such as firewall blocking the connection, network congestion, or misconfiguration of network settings can prevent the client from establishing a connection to the database.
• Resource Limitations: The listener process might have reached its maximum capacity for handling incoming connections, resulting in new connection requests being rejected.
• Listener Process Crash: The listener process might have crashed or encountered an internal error, causing it to terminate unexpectedly.

1. Troubleshooting:

• Check if the listener service is running on the database server by using the appropriate administrative tools or commands.
• Verify the listener configuration settings, including the listener name, protocol addresses, and service names, to ensure they are correctly configured.
• Review the listener log files for any error messages or warnings that might indicate the cause of the listener failure.
• Test the network connectivity between the client and the database server to ensure there are no network-related issues.
• Monitor system resource utilization (CPU, memory, etc.) on the database server to determine if resource limitations are causing the listener process failure.

1. Resolution:

• Restart the listener service on the database server to see if it resolves the issue.
• Check and correct any misconfigurations in the listener.ora file or the listener configuration settings.
• If network connectivity issues are identified, work with your network administrator to resolve them.
• If the listener process crashes persistently, consider analyzing any core dump files or contacting Oracle Support for assistance in diagnosing and resolving the underlying issue.

Resolving ORA-609 errors typically involves identifying and addressing the underlying cause of the listener process failure, which can vary depending on the specific circumstances of the error.