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| Log size for circular logging. |
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| kdorre |
 Posted: Wed Feb 12, 2003 2:32 pm Post subject: Log size for circular logging. |
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Novice
Joined: 17 Jul 2002
Posts: 15
Location: New Zealand
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All
Anyone out there got some advice on the number and size primary and secondary logs for a queue manager expected to handle up to 90 meg messages?
I am resolving some issues with MQ rolling back transactions because the logs are becoming full. This generally happens during times of peak processing. The MQ error log shows AMQ7469 and the application (Java) is getting 2003s.
Currently the queue manager has been defined with Linear Logging (the original consultant recommended this, however the reasons for choosing LL seem no longer valid) log size 4000 8 primary and 8 secondary. (It’s a windows platform)
My client is not averse to redefining the queue manager with circular logging as long as the message size can be handled. We did a quick snap shot and figured that the queue manager could possibly be handling 52 messages with an average size of 4 megs concurrently.
Advice would be greatly appreciated.
K |
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| bduncan |
| Posted: Wed Feb 12, 2003 2:46 pm Post subject: |
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Padawan
Joined: 11 Apr 2001
Posts: 1554
Location: Silicon Valley
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In addition to the fact that messages can be up to 90Mb, it is also very important to know what the throughput of these messages during peak times are. You mention the queue manager can handle about 52 4Mb messages concurrently. If we assume 1 second processing time, does your system come close to 50 messages per second during peak times? I've always preferred circular logging over linear logging. Bear in mind however that circular logging doesn't guarantee you won't run out of log space. If a single outstanding unit of work exceeds the total circular log size, the queue manager can't obviously start overwritting the same unit of work on top of itself, so it'll be forced to back the entire UOW out. So many people have asked about log size considerations... One of these days I need to sit down and write a real in depth article on it - if only I can find the time!
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Brandon Duncan
IBM Certified MQSeries Specialist
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| kdorre |
| Posted: Wed Feb 12, 2003 6:43 pm Post subject: |
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Novice
Joined: 17 Jul 2002
Posts: 15
Location: New Zealand
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Brandon
From what I can tell processing does take a long time, which makes the log situation more critical.
I have seen some of the larger files, 18 meg zipped, take approx an hour to process. Let’s just say the system has to do a lot with the incoming data!
However the design of the system says that if a message has failed we will try again. Usually the message will process after that because system activity has decreased.
Am I correct in (roughly) calculating that the parms
-ll -lf 1000 -lp 10 & -lp 10 will give me approx 40 meg primary and 40 meg secondary? This was the original config of the qmgr on windows.
So I think maybe redefining the queue manager to have lc –lf 4000 –lp 15 & -ls 15 might give me enough.
I’m sure that log sizing is not the black art that it seems to be, however a little more guidance from the IBM manuals would be helpful I suppose.
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| bduncan |
| Posted: Thu Feb 13, 2003 10:57 am Post subject: |
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Padawan
Joined: 11 Apr 2001
Posts: 1554
Location: Silicon Valley
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Yeah, the manuals seem to be a little deficient when it comes to log sizing considerations. Rather than worry about possible failures, and rather than sitting down and doing extensive calculations to come up with a precise configuration, I've tended to err on the side of caution and use a large number of secondaries (near the maximum of 63 I believe). If all goes well, most of those should never get allocated. And I can look at the number that have been allocated after a long period of time, and this can give me a decent measuring stick of what my peak activity required in the way of logs (because secondaries are never deallocated).
And yes, the logs are 4Mb per "unit", so if you set 10, you should end up with 40Mb log files...
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Brandon Duncan
IBM Certified MQSeries Specialist
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| kdorre |
| Posted: Thu Feb 13, 2003 11:46 am Post subject: |
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Joined: 17 Jul 2002
Posts: 15
Location: New Zealand
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Brandon
Thanks for that.
I will take the large and many approach
K
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| TonyD |
| Posted: Thu Feb 13, 2003 1:53 pm Post subject: |
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Knight
Joined: 15 May 2001
Posts: 540
Location: New Zealand
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| Supportpac MP16 (Capacity Planning and Tuning for MQSeries for OS/390!) has a section on the Log Manager (Appendix B). I don't know how applicable this is to MQ logging on Unix platforms but, after allowing for the obvious differences, I found it useful. After all, the MVS log is circular, and the data that is logged is basically the same. |
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