[MQ 9.3.0 Jun 2022]

Stream queues and transactions

The streaming queues feature allows a message put to one queue, to be duplicated to a second queue. In most cases the two messages are put to their respective queues under a unit of work.

If the original message was put using MQPMO_SYNCPOINT, the duplicate message is put to the stream queue under the same unit of work that was started for the original put.

If the original was put with MQPMO_NO_SYNCPOINT, a unit of work will be started even though the original put did not request one. This is done for two reasons:
  1. It ensures the duplicate message is not delivered if the original message could not be. The streaming queues feature only delivers messages to stream queues if the original message was also delivered.
  2. There can be a performance improvement by doing both puts inside a unit of work
The only time the messages are not delivered inside a unit of work is when the original MQPUT is non-persistent with MQPMO_NO_SYNCPOINT, and the STRMQOS attribute of the queue is set to BESTEF (best effort).
Notes:
  1. The additional put to the stream queue does not count towards the MAXUMSGS limit.
  2. In the case of a queue configured with STRMQOS(BESTEF), failure to deliver the duplicate message does not cause the unit of work to be rolled back.