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| AlexeiSkate |
 Posted: Wed May 15, 2002 7:12 am Post subject: Question on Log file size |
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Centurion
Joined: 10 Apr 2002
Posts: 123
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Hi,
The 'LogFilePages' represents the number of 4KB pages in the log file. So let say that I have 'LogFilePages = 256' and 'LogPrimaryFiles = 3' and 'LogSecondaryFiles = 2'. Does this mean that:
1) I have a total of 5 physical log files defined -3 primary and 2 secondary
2) each log file can contain up to 256 pages, with each page being 4KB
3) each log file size is 1024MB.
thanks,
Alex |
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| jhalstead |
| Posted: Wed May 15, 2002 8:08 am Post subject: |
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Master
Joined: 16 Aug 2001
Posts: 258
Location: London
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Agreed, upto 5 log files can be created (if this is a circular setup).
However 4Kb *256 is 1Mb.
So upto 5Mb of space will be used for logs.
Obviously if you go for linear loggin more log files will be created as the space is used.
Jamie |
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| AlexeiSkate |
| Posted: Wed May 15, 2002 9:23 am Post subject: |
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Centurion
Joined: 10 Apr 2002
Posts: 123
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Thanks for the reply.
So let say I have a maximum of 500,000 messages. Each msg is about 350 bytes in length. If I use persistant msg, then each msg will have an additional 750 bytes overhead. Not taking into account the other overhead required for actions like syncpointing and committing, does this mean that I need a total of about 537MB total to handle all of my messages ?
((350 bytes/msg + 750 overhead bytes/msg) * 500000 msg ) * 1MB/1024000 bytes
The max number of primary log files is 62 and for secondary is 61. So a total of 123MB size can be allocated for the log files. Assuming I will be using circular logging, how do I determine how many primary and secondary log files to allocate ?
I want to upload my file onto a queue as an all or nothing process. I'm not sure if I need to make the msg persistant though. If I make my msgs non-persistent, I don't think I have to worry so much about log files size. |
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| bduncan |
| Posted: Wed May 15, 2002 9:42 am Post subject: |
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Padawan
Joined: 11 Apr 2001
Posts: 1554
Location: Silicon Valley
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Alexei,
While you are correct when you say "max number of primary log files is 62 and for secondary is 61", that doesn't necessarily mean you are limited to 123MB of log files. If you look at the default settings for a queue manager, you see:
LogPrimaryFiles=3
LogSecondaryFiles=2
LogFilePages=1024
This means that a log file consists of 1024 4K chunks, which means a single file is 4MB. Initially 3 of these will be created (for a total of 12MB) and up to two more will be created (for a total of 20MB).
Without increasing the number of primaries or secondaries, you can simply increase the number of pages that are in a single log file from 1024 to some other value. For instance, the settings:
LogPrimaryFiles=10
LogSecondaryFiles=5
LogFilePages=4096
Will create 10 16MB log files (for a total of 160MB) and up to 5 more (for a total of 240MB).
_________________
Brandon Duncan
IBM Certified MQSeries Specialist
MQSeries.net forum moderator |
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| muralidhar |
| Posted: Wed May 15, 2002 10:41 am Post subject: |
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Acolyte
Joined: 28 Feb 2002
Posts: 50
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I just want to add a extra line to the discussion going on. The number of primary log files can be between 2 and 62 and secondary log files can be between 1 and 61.
But the limits for total number of primary and secondary log files together are 3 and 63. |
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| AlexeiSkate |
| Posted: Wed May 15, 2002 3:09 pm Post subject: |
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Centurion
Joined: 10 Apr 2002
Posts: 123
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Thanks for everyone's reply. It has been very helpful for me.
- Alex |
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| mrlinux |
| Posted: Thu May 16, 2002 3:34 am Post subject: |
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Grand Master
Joined: 14 Feb 2002
Posts: 1261
Location: Detroit,MI USA
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You can specify at QMGR create time the log files to be 64mb each. So you can have quite a bit of log space.
NOTE: if you are using MQSeries v5.1 or lower you may not be able to
get full log space from above due to shared memory restrictions of your OS.
HPUX = 1.75gb (assuming no other application is using shared mem )
Sun = 2.0gb
AIX = 2.5gb
Version v5.2 of MQSeries no longer maps logs into shared memory, so now the only restriction is disk space.
_________________
Jeff
IBM Certified Developer MQSeries
IBM Certified Specialist MQSeries
IBM Certified Solutions Expert MQSeries |
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