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DB2 - Problem description

Problem IT40066 Status: Closed

DECREASE DEFAULT MAX NUMBER OF THREAD TO 1023 INSTEAD OF 1024 ONAIX

product:
DB2 FOR LUW / DB2FORLUW / B50 - DB2
Problem description:
There is a limitation on AIX that maximum number of operations
per semop() call is 1024, thus we can not have more than 1024
threads in a db2fmp process on AIX. otherwise we can get to hang
with fmp due to limit of semaphore call.
AIX document regarding its limit:
https://www.ibm.com/docs/en/aix/7.1?topic=parameters-interproces
s-communication-tunable
Technote about fmp hang on AIX:
https://www.ibm.com/support/pages/db2fmp-hang-or-memory-issue

Currently we set the default max thread number to 1024 on AIX,
however this number is for worker thread, and because we already
have a master thread in threaded fmp process, so we may end up
with more than 1024 threads in a fmp process and cause hang.
We will always fail to create the last(1024th) worker thread
then repeat the creation and fail, and eventually these defunct
threads will still stay in fmp process and lead to a fmp process
with more than 1024 threads.
Thus we need to decrease the default max thread number by one to
ensure the total max thread number is 1024 in fmp process.
Problem Summary:
****************************************************************
* USERS AFFECTED:                                              *
* SP users                                                     *
****************************************************************
* PROBLEM DESCRIPTION:                                         *
* See Error Description                                        *
****************************************************************
* RECOMMENDATION:                                              *
* Upgrade to Db2 11.5.7.0 or higher.                           *
****************************************************************
Local Fix:
set up 'DB2_MAX_THREADS_PER_FMP' less than 1024.
Solution
Workaround
****************************************************************
* USERS AFFECTED:                                              *
* SP users                                                     *
****************************************************************
* PROBLEM DESCRIPTION:                                         *
* See Error Description                                        *
****************************************************************
* RECOMMENDATION:                                              *
* Upgrade to Db2 11.5.7.0 or higher.                           *
****************************************************************
Comment
See Error Description.
This issue was fixed in 11.5.7 or higher.
Timestamps
Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :
24.02.2022
06.07.2022
06.07.2022
Problem solved at the following versions (IBM BugInfos)
Problem solved according to the fixlist(s) of the following version(s)
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