ORA-32827: Messaging Gateway agent must be shut down
Cause: An operation was attempted that requires the Messaging Gateway agent to be shut down
Action: Issue SHUTDOWN, wait for MGW_GATEWAY view to show a NOT_STARTED status, and retry the operation. CLEANUP_GATEWAY may need to be issued to reset the gateway state if the agent fails to shut down after a reasonable time period
https://support.oracle.com/
http://www.oracle.com/