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The intra-group queuing agent and Serialization

 

If there is a failure of a queue manager in a queue-sharing group while the IGQ agent is dealing with uncommitted messages on a shared queue or queues, the IGQ agent ends, and shared queue peer recovery takes place for the failing queue manager. Because shared queue peer recovery is an asynchronous activity, this leaves the possibility for the failing queue manager, and also the IGQ agent for that queue manager, to restart before shared queue peer recovery is complete. This in turn leaves the possibility for any committed messages to be processed ahead of and out of sequence with the messages still being recovered. To ensure that messages are not processed out of sequence, the IGQ agent serializes access to shared queues by issuing the MQCONNX API call.

An attempt, by the IGQ agent to serialize access to shared queues while peer recovery is still in progress might fail. An error message is issued and the IGQ agent is put into retry state. When queue manager peer recovery is complete, for example at the time of the next retry, the IGQ agent can start.

 

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