Expired messages

Messages that have expired are discarded by the next appropriate MQGET call. However, if no such call occurs, the expired messages are not discarded, and, for some queues, particularly those where message retrieval is done by MessageId, CorrelId, or GroupId and the queue is indexed for performance, a large number of expired messages can accumulate. The queue manager can periodically scan any queue for expired messages, which are then deleted. We can choose how often this scanning takes place, if at all. There are two ways of doing this:

Explicit request

We can control which queues are scanned and when. Issue the REFRESH QMGR TYPE(EXPIRY) command, specifying the queue or queues that you want to be scanned.

Periodic scan

We can specify an expiry interval in the queue manager object by using the EXPRYINT attribute. The queue manager maintains information about the expired messages on each queue, and knows at what time a scan for expired messages is worthwhile. Each time that the EXPRYINT interval is reached, the queue manager looks for candidate queues that are worth scanning for expired messages, and scans only those queues that it deems to be worthwhile. It does not scan all queues. This avoids any CPU time being wasted on unnecessary scans.

Shared queues are only scanned by one queue manager in the queue-sharing group. Generally, the first queue manager to restart or the first to have the EXPRYINT set performs the scan.

Note:

You must set the same EXPRYINT value for all queue managers within a queue-sharing group.