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| Message Grouping Clarification |
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| sclarke |
 Posted: Thu Aug 18, 2005 5:14 am Post subject: Message Grouping Clarification |
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Apprentice
Joined: 05 Jan 2002
Posts: 39
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I would like to clarify my understanding of message grouping and commit. I have never used message grouping before and am trying to gain understanding before proposing using it in a design.
1. Application will create messages with PMO option of first message in group and tag last message in group as appropriate plus MQPMO_LOGICAL_ORDER and MQPMO_SYNCPOINT so that all messages are part of a unit of work and defined as a part of a group.
2. Receiving application will have MQGMO_ALL_MSGS_AVAILABLE and MQGMO_LOGICAL_ORDER
Say the destination queue is a remote queue, the putting application will commit the UOW but a single message may for some reason end up on the DLQ or be delayed – in this case – what is physically committed to the destination queue and available to the application? Is it an impartial set of messages? Will that ‘group’ only be available to the mqget when it is actually 100% complete? What happens when the missing message finally arrives (say 1 hour later)? Does the receiving application bypass that group until it is complete?
Thank you in advance for any input…… |
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| hopsala |
| Posted: Thu Aug 18, 2005 5:52 am Post subject: |
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Guardian
Joined: 24 Sep 2004
Posts: 960
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It all depends, really. If you MQGET by GroupID, with MQGMO_ALL_MSGS_AVAILABLE, and parts are missing, then you will get 2033 - MQRC_NO_MSG_AVAILABLE.
Once all msgs are in place, and you call another MQGET, you will get all msgs one by one, in the correct order (LOGICAL_ORDER).
So, until all msgs within the group are delivered, the receiving application gets nill. Only full groups will be delivered to the appl.
Keep in mind, that unless you know in advance the GroupId that you are going to receive, you always get the first msg without knowing anything; only after that you may get by groupid.
As per you other question about commits - when the sending appl works by syncpoint it only commits to the XMITQ, after that the msgs are, from the QM's point of view, completely independant; the channels have no idea these are parts of a logical group.
Best thing you could do, is try the scnearios out yourself. Download the put utility support pack, and start making experiments, this is the fastest way to learn. |
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| bower5932 |
| Posted: Thu Aug 18, 2005 6:30 am Post subject: |
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Jedi Knight
Joined: 27 Aug 2001
Posts: 3023
Location: Dallas, TX, USA
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