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| Maintaining Message Sequence across QM's in MQSeries |
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| Yuvaraj |
 Posted: Mon Nov 24, 2003 9:14 am Post subject: Maintaining Message Sequence across QM's in MQSeries |
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Apprentice
Joined: 28 Oct 2003
Posts: 30
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Hi All
Can anyone let me know whether Sequencing of messages flowing across two Queue Manager is possible using MQSeries or not?
I went through some of the MQSeries documents on Channels and they were talking about PipeLines. Let me put my understanding on the working of the Channels and the Pipelining of Channels.
Say the Batch size on the Channel is set as 1 and that all the messages are Persistance with the same priority. Then -
As per what I understand, the MCA on the Sending end of the Channel sends a message, followed by a confirmation and waits for the acknowledgement from the Receiving QueueManager before sending the next message. If this is the case then I would say that my channel is Synchronous and the message sequence should be maintained.
By Pipelining the channel I am reducing the waiting period of my Non-Persistant message which doesn't require any confirmation or acknowledgement from my Recieving end. This path is meant only for Non-Persistant message.
So in a way I am saying that Sequencing could be maintained in MQSeries if I configure my Channel and Message in the following way:
- All the Messages are persistance
- All the messages are of same priority
- Batch size on my Channel is 1
- PipeLine can be 1 or more
Please let me know if my understanding is right or I have missed out something?
Thanks & Regards
Yuvaraj |
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| bower5932 |
| Posted: Mon Nov 24, 2003 9:54 am Post subject: |
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Jedi Knight
Joined: 27 Aug 2001
Posts: 3023
Location: Dallas, TX, USA
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There is a discussion on "Sequential Retrieval of Messages" in the Intercommunication manual. It gives quite a few conditions that must be met:
| Quote: |
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.
Note: 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. |
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