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Sequential retrieval of messages

 

If an application puts a sequence of messages to the same destination queue, those messages can be retrieved in sequence by a single application with a sequence of MQGET operations, if the following conditions are met:

• All of the put requests were done from the same application.

• All of the put requests were either from the same unit of work, or all the put requests were made outside of a unit of work.

• The messages all have the same priority.

• The messages all have the same persistence.

• For remote queuing, the configuration is such that there can only be one path from the application making the put request, through its queue manager, through intercommunication, to the destination queue manager and the target queue.

• The messages are not put to a dead-letter queue (for example, if a queue is temporarily full).

• The application getting the message does not deliberately change the order of retrieval, for example by specifying a particular MsgId or CorrelId or by using message priorities.

• Only one application is doing get operations to retrieve the messages from the destination queue. If this is not the case, these applications must be designed to get all the messages in each sequence put by a sending application.

Messages from other tasks and units of work may be interspersed with the sequence, even where the sequence was put from within a single unit of work.

If these conditions cannot be met, and the order of messages on the target queue is important, then the application can be coded to use its own message sequence number as part of the message to assure the order of the messages.

 

Parent topic:

Channel message sequence numbering

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