A MONITOR_EVENTQ request allows you to start (ACTION=START) or stop (ACTION=STOP) monitoring your event queue for the presence of event monitor controls (EMCs). The system queues or withdraws event monitor controls on your event queue when sublist monitoring is in effect. The EMCs indicate the empty or nonempty state of the sublist(s) that you are monitoring.

When starting event queue monitoring, you must specify the list notification vector index (VECTORINDEX) to be associated with the event queue. List services uses the specified vector index to indicate whether the event queue is in the empty or non-empty state.

If you want to be notified when the event queue for which monitoring has been activated has changed state from empty to non-empty, specify DRIVEEXIT=YES. This option causes your list transition exit to be driven, informing you that your monitored event queue now has at least one entry on it. You must identify your list transition exit on the LISTTRANEXIT parameter of the IXLCONN macro. You can use the IXLVECTR macro to test the vector entry that you have associated with your monitored event queue.

A MONITOR_EVENTQ request can be issued only for keyed list structures allocated in a coupling facility of CFLEVEL=3 or higher. MONITOR_EVENTQ requests issued for a list structure allocated in a coupling facility of CFLEVEL 0, 1, or 2 will fail.

If you have started event queue monitoring with a certain vector index specified and you want to monitor the event queue with a different vector index, do not stop monitoring the event queue with the old vector index. Simply start monitoring the event queue with the new index; the new index will automatically replace the old.