You should use a message queue monitor when you need to watch a message queue for the occurrence of certain message IDs. Message queue monitors are appropriate for situations where a process or an application sends messages to a specific message queue.
For example, you may want to monitor the primary message queue used by MIMIX for messages indicating that a file has been placed on hold and notify the system operator when this occurs. Or, you may want to monitor the system operator message queue for messages indicating user profiles that have been disabled because the number of invalid sign-on attempts has been exceeded. You could have an event program send a break message to the operator, or automatically reset the user profiles, or run an additional security program.
Additionally you could have a monitor watch for certain messages in the system operator message queue and automatically recycle controllers.