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2 replies Latest Post - ‏2012-10-23T14:04:19Z by satvm
1 Post

Pinned topic AIX 6.1 Tuning Asynchronous I/O

‏2012-07-17T10:37:20Z |
AIX 6.1.0 Oracle 11G

uknwsaviv705:keoghs1:/home/users/keoghs1 $ oslevel -s

Oracle Database 11g Enterprise Edition Release - 64bit Production

uknwsaviv705:keoghs1:/home/users/keoghs1 $ iostat -A

System configuration: lcpu=8 drives=12 ent=0.40 paths=24 vdisks=2 maxserver=640

aio: avgc avfc maxgc maxfc maxreqs avg-cpu: % user % sys % idle % iowait physc % entc
1.1 0.0 742 0 24 1.8 2.0 96.0 0.2 0.0 6.3
Is there a need to increase maxreqs on AIX 6.1 when maxgc is greater than maxreqs or is AIX 6.1 expected to auto-tune this value ...


Updated on 2012-10-23T14:04:19Z at 2012-10-23T14:04:19Z by satvm
  • SystemAdmin
    6902 Posts

    Re: AIX 6.1 Tuning Asynchronous I/O

    ‏2012-10-23T10:20:57Z  in response to StephenKeogh
    Hi to everybody at the forums.

    I have not the answer, but maybe I can add some thoughts to this thread.

    The 'maxreqs' output from 'iostat -A' anyone can see now with AIX 6.1 and higher levels of AIX 5.3 is always the result of 'aioservers running

    The output provided by StephenKeogh seems to indicate that the partition is running 24 aioservers (check with classical pstat -a |grep aioservers), the
    result comes from 8*3. I suppose from the output that you have provided that your aio_maxservers is 80.

    Has no direct relation to aio_maxreqs kernel parameter, I think the relation is relative.
    As far as I am seeing within instances of AIX with Oracle 11.2... is that
    manpage and publib.boulder... seem to have not an accurate information about that particular issue or, more probably, I am missing something.

    The weird thing for me is checking that 'filesystemio_options' oracle parameter into spfile of such an instance
    is 'setall' and having that operations from Oracle are 'cio' style, then, having aio_fsfastpath activated, as it is the
    default value on AIX 6.1, then the 'avfc/maxfc' should be greater than zero sooner or later, but I allways see that only 'avgc/maxgc' increasing and
    only a few aio_servers running, but they seem to run for any other reason not for providing asynchronous access to database in a regular basis. I see
    aio servers active only when RMAN archivelogs backups are being sent to TSM.

    I cannot test to disable fsfastpath and check if something changes into those counters as it did in the past.

    I see no application of current publications as "SC23-5261-02/Kernel Extensions and Device Support
    Programming Concepts" or redbooks to be completely true on AIX 6.1 instances.

    I hope it is my own misunderstanding and help pointing some documentation or tips would be highly appreciated.
    • satvm
      2 Posts

      Re: AIX 6.1 Tuning Asynchronous I/O

      ‏2012-10-23T14:04:19Z  in response to SystemAdmin

      In AIX Version 6, all AIO subsystems parameters become the ioo command tunables.

      You can see the curent values using i00 command

      1. ioo -a | grep aio
      aio_active = 0
      aio_maxreqs = 65536
      aio_maxservers = 30
      aio_minservers = 3
      aio_server_inactivity = 300
      posix_aio_active = 0
      posix_aio_maxreqs = 65536
      posix_aio_maxservers = 30
      posix_aio_minservers = 3
      posix_aio_server_inactivity = 300

      In the above output, 65536 is the default value of maxreqs and the maximum is 1,048,576.
      Hope this helps.