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  • 1.  How many CPU do i need ?

    Posted Wed June 30, 2021 03:23 PM
    Hello to All

    Question : How can  i determine how many CPU cores do i need on a Server ?

    I Have 2 CPU used (dedicated + uncapped mode) on a 4 CPU pool, and Informix sometimes uses more than the 2 CPU , (3,5)

    can i configure informix to use only the 2 CPUs, or should i increase the number  of CPU ?

    Thanks in advance

    John Smith


  • 2.  RE: How many CPU do i need ?

    IBM Champion
    Posted Wed June 30, 2021 05:26 PM
    More important than that the engine caused the VM to add more CPU cores is how busy they were. What does mpstat -P ALL show for each core as %idle? Remember, even if you only configure a single CPU VP, there are still the ADM VP, MSC VP, AIO VPs, NET VPs, etc. If the two cores are busy enough the VM is going to allocate additional cores, but that doesn't mean they were running close to 100%!

    Now, you actually may need more cores, but if you don't, the only way to limit the number of cores that get assigned a VP to run is to limit the number of cores and not let them float. Also, don't forget your license requirements. How many cores are you licensed for? If it is the PVU level for 4 cores then make those four dedicated, if it's only 2 then you are out of compliance is you don't limit the VM to two cores only.


    Art S. Kagel, President and Principal Consultant
    ASK Database Management Corp.

  • 3.  RE: How many CPU do i need ?

    IBM Champion
    Posted Thu July 01, 2021 03:02 AM
    Hi John,

    If it is a VM, then it is also important to check if the cores are 100% exclusively dedicated to the VM (i.e. pinned). Many VM admins love to assign the machines as "overcommit". This should never the case for a DB server.


    Henri Cujass
    leolo IT, CTO
    IBM Champion 2021