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| Messages, Buffer, PSID and Logcopy |
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| bay hoe san |
 Posted: Mon Sep 03, 2007 6:52 pm Post subject: Messages, Buffer, PSID and Logcopy |
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Centurion
Joined: 27 Nov 2006
Posts: 117
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Hello,
( 1) Say if we configure a qmgr with the following confiugrations:
- buffer = 1, PSID = 1 cyl, Logcopy = 1 cyl
( 2) My doubts/queries:
1. When the buffer is full, the msgs will over flow to PSID. When buffer and PSID is full, it will overflow to Logcopy and if logcopy is full it will be archive. Assuming uncommitted msgs pending to be consume. Is the above correct?
2. Is the above applicable to persistent and/or non-persistent
msgs?
Pls advise.
Thanks.
.Hoe San. |
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| fjb_saper |
| Posted: Mon Sep 03, 2007 7:49 pm Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20756
Location: LI,NY
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There is an excellent part (don't remember if it is a redbook or a manual) about sizing MQ for zOS.
Read it. 
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MQ & Broker admin |
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| Mr Butcher |
| Posted: Mon Sep 03, 2007 9:50 pm Post subject: |
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Padawan
Joined: 23 May 2005
Posts: 1716
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in the past you showed up with quite a few z/OS related MQSeries questions.... from the questions you asked i recommend you do some more reading to get a better overview of mqseries.
i understand your questions well, but i.m.h.o most of them could be answered by reading the mq manuals and the available redbooks to get a better overview of the product, its functions and the way it works.
so read - read - read !!!!
related to your question:
no one will configure a queuemanager that restricted way. anyway, messages are stored in pageset buffers (buffer pools) first. The buffer pool is not an additional sotrage for the message, it is used for performance reasons. even if a message is placed into the buffer pool there must be space in the pageset for them. you can get a "queue full" or "pageset full" condition even if the message is still in buffer.
now at certain conditions messages are rolled out from the bp to pageset
- bp is short of storage (you will get a csq... message for it)
- 2 checkpouints have passed
- ?
(dont remember all conditions exactly, check the manuals)
the archive log is a different thing. this is the place where units of work are recorded, so that backout or recovery can be performed.
if there is a unit of work the proper logging records are placed in the log buffer. at commit time, the related log records are written to the active log on dasd. why? the message may still be in the buffer pool, if mq crashes now it is lost. but with writing the log records to the active log the persistent message is available for recovery now.
when the active log becomes full mq switches to the next available active log file and the full one gets archived.
if there are uows that are still active and hit the archive log then mq will tell you (long running uow found), because this is an performance issue in case of recovery needed (mq has to read the archive log then).
non persistent messages are not recorded in the log.
so buffer pool and pageset is one part, used to store messages in a performant way.
log buffer, active log and archive log is a secend part, used to collect and maintain backout and recovery information.
although both parts are involved in a mqseries uow, there is no overflow of the pageset to active or archive log. !!
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Regards, Butcher |
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| bay hoe san |
| Posted: Tue Sep 04, 2007 7:32 pm Post subject: |
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Centurion
Joined: 27 Nov 2006
Posts: 117
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Hello Mr. Butcher,
( 1) I have read most of the MQ documentation and some times I rely on the website and most impt, all your guidance for info. However, at times, I am in doubt and a bit confuse when I read more and hence I approach experts like u out there in the cyberspace for guidance and advice.
( 2) Once again, I would like to express my sincere appreciation for all those that have given me advice and guidance. I have learnt a lot indeed.
Thank you.
.Hoe San. |
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