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| When are checkpoints written to log files |
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| Boomn4x4 |
 Posted: Mon May 12, 2014 4:44 am Post subject: When are checkpoints written to log files |
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Disciple
Joined: 28 Nov 2011
Posts: 172
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I'm using linear logging and have a process that runs nightly to maintain the log files, deleting log files that are no longer necessary for restart. I was under the impression that MQ routinely maintains itself by putting check points into the log files and advancing the logs on its own. In my initial testing, this was the case. However, now that there are a few thousand servers running, I'm seeing that in about a half dozen instances, the log files advance, but the maintenance script isn't picking up a checkpoint as it is keeping all of the log files as being archive-eligible.
I'm sure that the fix is to recmqimg on a daily basis, but I've also read that doing so can be resource intensive. Am I wrong in that MQ will put its own check points in and that logs will eventually become deleteable or is a recmqimg necessary? If so, then why are an overwhelming majority of my servers deleting old logs just fine w/o a recmqimg? |
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| Vitor |
| Posted: Mon May 12, 2014 4:55 am Post subject: Re: When are checkpoints written to log files |
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Grand High Poobah
Joined: 11 Nov 2005
Posts: 26093
Location: Texas, USA
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| Boomn4x4 wrote: |
| Am I wrong in that MQ will put its own check points in and that logs will eventually become deleteable or is a recmqimg necessary? |
AFAIK WMQ will checkpoint the logs for message recovery according to it's configuration but media images are only taken when an rcdmqimg is issued. This seems to be confirmed here by this comment:
| Quote: |
| rcdmqimg must be run manually or from an automated task you have created. The command does not run automatically as it must be run in accordance with, and as determined by, the usage of each individual customer of WebSphere MQ |
| Boomn4x4 wrote: |
| If so, then why are an overwhelming majority of my servers deleting old logs just fine w/o a recmqimg? |
There's a bug in your script? Have you tried recreating an object and/or a queue manager from one of theses servers to demonstrate that none of these deleted logs are actually needed?
_________________
Honesty is the best policy.
Insanity is the best defence. |
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| Vitor |
| Posted: Mon May 12, 2014 5:05 am Post subject: Re: When are checkpoints written to log files |
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Grand High Poobah
Joined: 11 Nov 2005
Posts: 26093
Location: Texas, USA
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| Boomn4x4 wrote: |
| I've also read that doing so can be resource intensive. |
Where? Post a link
Why is resource intensive a problem? If it uses 80% of the server's CPU but only for 10 seconds, that's not a problem.
Also you talk a nightly process that runs to maintain the log files. Note only does it seem to be a trivial task to include the command as the first step of this process, it impiles a nightly window where server performance is "degraded" by this administrative task running anyway. In my world, this is called a "maintenance window" and users are aware that performance may be degraded to sub-SLA levels during this published timeslot.
For example, we do this to 3 Prod servers in a particular system which is 24x7x365 and a sub second responce (according to the users) will cause the sky to turn to fire, the seas to blood and 4 guys on horseback to enter the parking lot. The WAS people need to do something Java-ish on a nightly basis that causes WAS to basically sit and scratch itself for about 10 minutes burning CPU. So all this fun kicks off at 3am and the users are advised that the system will be degraded 3am - 4am. One server starts at 3am, another starts at 3:20 and another at 3:40 and non-one has ever complained about poor response because 2 servers can easily handle the load when all of our sensible customers are asleep.
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