AIX

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  • 1.  AIX with DB2 - CPU ENTITLEMENT, CPU USAGE

    Posted Fri March 25, 2022 09:51 AM
    Hi Community,

    I have a AIX environment with a db2 database installed.

    So far we have feeling a degradation performance from the database.
    Things we checked:
    • CPU entitledment configured is 0.2
    • CPU entitledment consumed is 1.9
    • DB2 CPU Usage is 700%,800%, etc.
    After check this document:
    I conclued that CPU value are not good.

    How can I fix this?

    Thanks in advance.

    Regards.

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    Filipe Ventura
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  • 2.  RE: AIX with DB2 - CPU ENTITLEMENT, CPU USAGE

    Posted Fri March 25, 2022 10:51 AM

    Hello Filipe,

    How much is your virtual CPUs configured ?

    What is your hardware  P7, P8, P9 ?

    Not sure how big and loaded  is your DB2 database , but it looks like for database 0.2 Physical CPU is too low .

     

    ON  Power 7 smt 4 is enabled by default

    Recommended  Ratio Entitled (Physical  CPU)  capacity to virtual 1 :8

    Power8 onward

     SMT8 is enabled by default

     So IBM recommending to reduce virtual CPUs on P8 onwards ,  so ratio becomes 1: 4

    But so far customer are not understanding SMT4 vs SMT8  .. so relying on SAP or DB2 / Oracle's   vendors  old recommendations .. and asking more virtual CPUs  .. ending up with degraded performance .

    You can adjust/ increase  your CPU's   configuration  accordingly

     

    • CPU entitledment configured is 0.2
    • CPU entitledment consumed is 1.9
    • DB2 CPU Usage is 700%,800%, etc.

     

    Thanks,

    Afzal Muhammad

     

    IBM Certified AIX System Administrator AIX 6.1

    IBM Certfied AIX System Administrator AIX 4.3

    IBM Certified WebSphere 6.0 Adminstrator

    Red Had Linux 7 Certified  System Administrator (RHCSA)

    Global pSeries platform services – AIX

    Ford Motor Company,  Dearborn Michigan

    United States of America

    Tel: Cell 1-704-492-0586

    Email: mafzal10@ford.com

     






  • 3.  RE: AIX with DB2 - CPU ENTITLEMENT, CPU USAGE

    Posted Sun March 27, 2022 09:31 PM
    This is changed from the HMC.
    There’s a “profile” that you need to change to have the value survive a power cycle.
    and there’s a running “live” value. There’s ways to change both at once, but just be aware there are two places it’s stored.

    Tom




  • 4.  RE: AIX with DB2 - CPU ENTITLEMENT, CPU USAGE

    Posted Wed March 30, 2022 06:57 AM
    Hi,

    IBM's recommendation is to not use profiles anymore unless you have some unusual requirements. Just change "Current" and leave it at that.

    Sadly, that only works if everyone in your organisation is enlightened, as I found out.

    Regards,
    Henrik Morsing

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    Henrik Morsing
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  • 5.  RE: AIX with DB2 - CPU ENTITLEMENT, CPU USAGE

    IBM Champion
    Posted Thu March 31, 2022 04:52 AM
    • CPU entitledment configured is 0.2 <- This means that above 0.2 CPU, the LPAR is competing with every other uncapped LPAR for CPU.
    • CPU entitledment consumed is 1.9 <- If you only have 2 VPs, the most the LPAR can consume is 2 CPU, so it may be banging against the ceiling.
    • DB2 CPU Usage is 700%,800%, etc. <- That's compared to the entitlement, so it's consuming between 1.4 and 1.6 CPUs.

      Increase the entitlement to something closer to the actual needs.  In this case, you should increase it to 1.6.
      Increase the number of VPs to have enough CPU slots to be able to go above the entitlement if needed.  If the LPAR is going up to 1.9 CPU and still feels slow, but there is no I/O problem, increase the number of VPs to at least 3.
      Check the disk performance.
      Set maxperm&maxclient to 10%. (DB2 doesn't use the file cache)


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    José Pina Coelho
    IT Specialist at Kyndryl
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