Informix

  • 1.  CPU efficiency

    Posted 17 days ago
    Hello

    seen with onstat -g glo on a heavy OLTP server , CPU efficiency is about 40% ?
    do i need to change some parameters (VPCLASS CPU ...other ?)

    Thanks

    ------------------------------
    John Smith
    ------------------------------


  • 2.  RE: CPU efficiency

    Posted 16 days ago
    Is this on a REAL machine or a Virtual machine?

    ------------------------------
    Jon Ritson
    ------------------------------



  • 3.  RE: CPU efficiency

    Posted 16 days ago
    Virtual machine
    regards

    ------------------------------
    John Smith
    ------------------------------



  • 4.  RE: CPU efficiency

    Posted 11 days ago
    Hi John,

    Is your Informix on cooked devices ? 
    Are you using ver 12.10 and above ?
    Do you notice sequential scans on system catalog tables (like sysdistrib etc) ?
    Do those tables appear top of the sequential counts ?

    We have noticed similar CPU (degraded) efficiency on our high OLTP DB.
    Also noticed that system catalog tables were doing lot of sequential counts

    We implemented the following:
    a) update statistics high on offending system catalog tables
    b) zero profile counts (onstat -z) 
    c) run find sequential scans query again
    It should now not show system catalog tables and your CPU efficiency will improve.

    Additional Note:
    If you are using AWS  EC2 instances, you can definitely see a big drop in the graph for "EBS: Average I/O across all volumes"

    PS: There is no 'official' documentation from IBM/HCL about updating system catalog tables. Please be aware of this and any side effects.

    HTH

    Regards
    Mallik

    ------------------------------
    Mallik Damaraju
    ------------------------------



  • 5.  RE: CPU efficiency

    Posted 10 days ago
      |   view attached
    Hi Mallik.

    It would be better also to resize schema caches so system catalog tables don't need continuous rereading. See DD_* DS_* PC_* in $ONCONFIG. The definitive IIUG presentation by Mark Jamison on this is attached.

    ------------------------------
    Doug Lawry
    Oninit Consulting
    ------------------------------

    Attachment(s)