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Undelivered/unprocessed messages

 

If an IGQ agent cannot deliver a message to the destination queue, the IGQ agent:

• Honours the MQRO_DISCARD_MSG report option (if the Report options field of the MQMD for the undelivered message indicates that it should) and discards the undelivered message.

• Attempts to place the undelivered message on to the dead letter queue for the destination queue manager, if the message has not already been discarded . The IGQ agent prefixes the message with a dead letter queue header (MQDLH).

If a dead letter queue is not defined, or if an undelivered message cannot be put to the dead letter queue, and if the undelivered message is:

• persistent, the IGQ agent backs out the current batch of persistent messages that it is processing, and enters a state of retry. For more information, see Retry capability of the intra-group queuing agent.

• non-persistent, the IGQ agent discards the message and continues to process the next message.

If a queue manager in a queue-sharing group is terminated before its associated IGQ agent has had time to process all its messages, the unprocessed messages remain on the SYSTEM.QSG.TRANSMIT.QUEUE until the queue manager is next started. The IGQ agent then retrieves and delivers the messages to the destination queues.

If the coupling facility fails before all the messages on the SYSTEM.QSG.TRANSMIT.QUEUE have been processed, any unprocessed non-persistent messages will be lost.

IBM recommends that applications do not put messages directly to transmission queues. If an application does put messages directly to the SYSTEM.QSG.TRANSMIT.QUEUE, the IGQ agent may not be able to process these messages and they will simply remain on the SYSTEM.QSG.TRANSMIT.QUEUE. Users will then have to use their own methods to deal with these unprocessed messages.

 

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