• 1 reply
  • Latest Post - ‏2013-03-25T21:43:49Z by nagger
4 Posts

Pinned topic nmon and async io

‏2013-02-28T15:49:19Z |

As I understand, Async IO in AIX 6.1 and 7.1 is being performed via fastpath for raw devices or FS with CIO option, but aioservers are being used for regular files without CIO. And aioservers are not used for AIO for files opened with CIO. Correct me, please, if I am mistaken.
NMON can show the aioservers statistics on PROCAIO sheet and can not show fastpath statistics. Is it correct?
Is there a way to see a statistics in NMON like "iostat -A" shows?

And one more question.
My filesystem with oracle datafiles mounted with CIO and I can see some amount of running aioservers in PROCAIO sheet (after analysing nmon data). Does it mean these AIO requests (processing aioservers) were not initiated by oracle but some others processes?

Thank you!
Updated on 2013-03-25T21:43:49Z at 2013-03-25T21:43:49Z by nagger
  • nagger
    1734 Posts

    Re: nmon and async io

    Asynchronous I/O is a programing technique and system calls that means the process or thread does not have to wait for the read or write calls. It is a "get on with these 200 I/O" and let be know when they finish.

    Director or Concurrent I/O allows the program to avoid the file system cache and thus avoid double buffering and memory waste.

    Very few applications or programs use Async I/O so it is probably Oracle.

    iostat -A stats - nope.
    Raise a PMR and ask for them.

    I hope that helps, Nigel Griffiths