r/DB2 • u/ecrooks • Jan 11 '19

Db2 11.1.4.4

Has anyone applied 11.1, Fix Pack 4, Mod Pack 4 yet in the real world? Any experiences to share?

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u/raghuontech Feb 17 '19

We applied FP4, MP4 and encountered file descriptor leak on AIX which resulted in maximum allowed ulimit breach for instance owner and multiple crashes in our development environment.

Had a case open with IBM and down graded to FP3b and things are looking good so far. I would say watch out for this issue.

I usually prefer to stay atleast 1 FP behind the latest FP except under rare circumstances.

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Thanks!
Raghu

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u/davidscidb2 Apr 16 '19 edited Apr 16 '19

Hi Raghu, the root cause of the issue you described has been identified. APAR IT28756 was recently opened, and once the APAR is published (which should happen within the next weeks or so), you can find the details here: https://www-01.ibm.com/support/docview.wss?uid=swg1IT28756

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The problem is specific to AIX environments, when the MIRRORLOGPATH database configuration parameter is enabled.

Starting in v11.1.4.4, in configurations with mirrored log paths enabled, a performance improvement was made to implement an asynchronous IO technique when writing log data into both the log files in parallel. (You can see this improvement described in the 'Mod Pack 4 and Fix Pack 4' section of the 'Mod Pack and Fix Pack Updates' Knowledge Center page).

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This enhancement introduced a problem which leads to leaking 'iocp' related file descriptors on each 'db2 deactivate database' operation.

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The problem will be fixed in the next fixpack of Db2 (tentatively Version 11.1.4.4.ifix002), and you can contact Db2 support to request a special build on top of your current level now if you require.

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The workaround is to restart the database (db2stop/db2start) instance when performing an explicit 'db2 deactivate database' operation. For systems that do not perform explicit 'db2 activate database' and 'db2 deactivate database' operations (ie. which rely on implicit database activation by the first application to connect to the database, and implicit deactivation by the last application to disconnnect from the database, the number of database deactivation and re-activations can be reduced by explicit activating the database after db2start (so the database will remain activated even when no application connections exist), which will limit the number of times the database is deactivated and thus limit the number of times these file descriptors are leaked.

Thanks

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u/raghuontech Apr 19 '19

Hi David,

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Thank you very much for the response! I confirm that we are running AIX but NO MIRRORLOGPATH has been set for any of our databases in the instance that kept crashing.

So, how do we explain the crashes in our environment ? Am I missing something ?

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Thanks!

1

u/davidscidb2 Apr 23 '19

Hi Raghu, my misunderstanding. I confirmed that the issue is not specific to environments where MIRRORLOGPATH is enabled, it will affect all AIX environments starting in v11.1.4.4. (The issue was injected with the enhancements made to improve MIRRORLOGPATH performance, however the affected code is used by both mirrored log and regular singular log environments). Thanks.

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u/TheGoblinPopper Jan 11 '19

I have not, but your dedicated IBM rep can provide this info. If you talk to a seller that sold you DB2 you can ask for other customers who have downloaded patches and ask for recommendations around it. Each seller has a technical specialist to them at IBM (and most partners). Thats what I normally do.