Rebuilding queue indexes

To increase the speed of MQGET operations on a queue where messages are not retrieved sequentially, we can specify that you want WebSphere MQ to maintain an index of the message or correlation identifiers or groupid for all the messages on that queue (as described in the WebSphere MQ Application Programming Guide).

When a queue manager is restarted, these indexes are rebuilt for each queue. This applies only to persistent messages; nonpersistent messages are deleted at restart. If your indexed queues contain large numbers of persistent messages, this increases the time taken to restart the queue manager.

We can choose to have indexes rebuilt asynchronously to queue manager startup by using the QINDXBLD parameter of the CSQ6SYSP macro. If you set QINDXBLD=NOWAIT, WebSphere MQ restarts without waiting for indexes to rebuild.