Listener refused the connection with the following error:ORA-12514

ORA-12514 is an Oracle database error that indicates the listener failed to connect to the database instance. This error can occur due to a number of reasons, such as:

1. Incorrect database name or service name specified in the connection string.
2. The database instance is not running or is not registered with the listener.
3. The listener is not configured properly.
4. The database instance is configured to use a different port than the default.

To resolve this error, you can try the following steps:

1. Verify that the database instance is running and registered with the listener using the lsnrctl status command.
2. Check the TNS listener configuration file (listener.ora) to ensure that the database name or service name is correctly specified.
3. Verify that the listener is configured to listen on the correct port. You can check this by looking at the listener.ora file or by using the lsnrctl services command.
4. Ensure that the database instance is configured to use the default port (1521) or the port specified in the listener.ora file.

If none of the above steps resolve the issue, you may need to contact your database administrator for further assistance.