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| velocity |
 Posted: Tue Aug 31, 2010 9:36 am Post subject: Active log files & space considerations |
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Centurion
Joined: 30 Nov 2007
Posts: 126
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Hi Guys:
We have failover to be done from one set of servers to another set. The volume is going to be doubled. These msgs are persistent. Currently the disk space allocated to /var/mqm looks like below:
/dev/hd9var 1048576 829436 21% 713 1% /var
/dev/ap1040 10485760 7954792 25% 1222 1% /var/mqm
/dev/ap1041 524288 128484 76% 57 1% /var/mqm/log
/var/mqm/log is 76% full and is 500 MB. I plan to make it 1 GB. Currently the QM is configured to use 12 promary and 3 secondary files. So after making the filesystem 1GB will I have to increase the number of logfiles also? What happens if /var/mqm/log becomes 100%? |
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| mqjeff |
| Posted: Tue Aug 31, 2010 9:59 am Post subject: |
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Grand Master
Joined: 25 Jun 2008
Posts: 17447
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Changing the diskspace has no affect on the qmgr log sizing, and vice versa.
You probably want to increase the diskspace to 1.25 or 1.5 GB, instead of merely 1GB.
If the disk holding the log gets full, MQ will start to complain to everything talking to it trying to do transactions and to it's error logs. The qmgr may even shut down. |
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| velocity |
| Posted: Tue Aug 31, 2010 10:10 am Post subject: |
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Centurion
Joined: 30 Nov 2007
Posts: 126
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Thanks a lot for the reply.
| Quote: |
Changing the diskspace has no affect on the qmgr log sizing, and vice versa.
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So when would I be required to increase the number of log files. When will I encounter a situation when the disk space full?
Thanks in advance... |
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| bruce2359 |
| Posted: Tue Aug 31, 2010 10:13 am Post subject: |
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Poobah
Joined: 05 Jan 2008
Posts: 9470
Location: US: west coast, almost. Otherwise, enroute.
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How to calculate log file size is well-documented in the WMQ System Admin manual.
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| exerk |
| Posted: Tue Aug 31, 2010 11:24 am Post subject: |
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Jedi Council
Joined: 02 Nov 2006
Posts: 6339
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And if your logging is circular (going by your post "...the QM is configured to use 12 primary and 3 secondary files..."), then you can calculate the amount of space that will be used if they all get used (log file size x 15) and see if that 1GB gives you enough head room - and don't forget to allow additional space 'just in case', disk is cheap these days.
As to when you encounter a situation when the disk space is full, that will be when the space you have allocated for the logs is insufficient for a new secondary log to be cut (see my comment above), and that is dependent on the behaviour of the applications connected to that queue manager, e.g. too-long-UOW's etc.
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| velocity |
| Posted: Tue Aug 31, 2010 11:46 am Post subject: |
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Centurion
Joined: 30 Nov 2007
Posts: 126
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Thanks a lot for your reply..
Yes, I am using circular logging...and logfile size * 15= 4MB*15=60MB?
Where am I going wrong here..? |
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| exerk |
| Posted: Tue Aug 31, 2010 11:58 am Post subject: |
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Jedi Council
Joined: 02 Nov 2006
Posts: 6339
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From the manual (V7.0 Info Centre):
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LogFilePages=number
The log data is held in a series of files called log files. The log file size is specified in units of 4 KB pages. The default number of log file pages is 4096, giving a log file size of 16 MB.
On UNIX systems the minimum number of log file pages is 64, and on Windows the minimum number of log file pages is 32; in both cases the maximum number is 65 535. |
So if you didn't size your logs correctly when you created the queue manager, you may need to increase the number of logs to compensate - better to have a small number of large logs than large number of small logs (personal opinion); if your logs were left at the default size, then the figure you're looking at is 240MB (note the size of log that 65,535 pages gives you  ).
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It's puzzling, I don't think I've ever seen anything quite like this before...and it's hard to soar like an eagle when you're surrounded by turkeys. |
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| Vitor |
| Posted: Tue Aug 31, 2010 11:58 am Post subject: |
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Grand High Poobah
Joined: 11 Nov 2005
Posts: 26093
Location: Texas, USA
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| velocity wrote: |
| Where am I going wrong here..? |
Potentially you're not.
The queue manager will use a maximum log space as you describe because that's the logging parameters it's using. Provided there's enough space to define those logs the queue manager will be happy. It will neither know nor care there's an extra 1Gb, 1.5Gb or 1Tb on the file system.
You will encounter a log full when the number of active transactions being logged exceeds that defined limit. At this point you'd need to increase the number of defined logs.
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Insanity is the best defence. |
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