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  1. #1
    Join Date
    Sep 2002
    Posts
    12

    Unanswered: how can i sure that the buffer is enough in Informix

    how can i sure in our system that the buffer size is enogh in our sytem?what percent of it in use and what percent of it available(free) at a particular time?Which commands can be used to get the answers to this issue?

    when i type onstat -g ioq command i see that there are 24 chunks in 72 chunks which exceeds maxlen 25. (for example 44,61,42,..etc).is it related the buffer size or AIO or is a result of unbalanced disk?

    system: IDS 7.31 FD1 on HP-UX 10.11
    some parameters:
    Buffer 400000
    LRU 127
    Cleaners 127
    AIO 40
    CPU 3 #3 for Informix,1 for Unix
    LRU_MIN %1
    LRU_MAX %2
    CHKPNT 180 #3 M,NUTES
    PHYLOGSIZE 500 MB
    LOGLOGSIZE 2 GB

  2. #2
    Join Date
    Aug 2002
    Location
    Belgium
    Posts
    534
    Hi,

    Normally, informix doesn't have any free memory in its resident part (BUFFERS).

    'onstat -g seg' shows you the main memory segments. The 'R' stands for resident? 'V' stands for virtual.

    The LRU (least recently used qeueus will throw the least recently used page out of memory to allow a new page in memory.

    'onstat -g ioq' maxlen will show you the meximum number of IO in qeu for that chunk since startup. It can be caused by a slow disk, or your main data is on one chunk. Or you don't have enough AIO virtual processors defined.

    In your case, your Buffer mem of 400000 will be devided into 127 (LRU) equal parts. If one of these parts exceeds 2% dirty, a cleaning process will start cleaning to disk. Check with onstat -F and onstat -R.
    rws

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