FAQ
Hi,

I been looking at some (10.2.0.4) on AIX 64 bit Awr report File IO Stats and
can see that the Av Rd(ms) for some of the files are consistently above 50
to 60 ms over a 15min interval but when I reported this storage guy he
mention and sent me the Iostat to prove that the service time in the same
timeline is average of 20ms for the disk involve . What can cause the
difference between the AWR and iostat readings

thanks

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  • Allen, Brandon at Aug 3, 2011 at 3:13 pm
    Maybe there is something else other than your Oracle instance that is also performing IO on the same disk so the stats for those IOs are being calculated in his averages, but not in AWR.

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  • K Gopalakrishnan at Aug 3, 2011 at 3:14 pm
    IO size between iostats and filestat.

    -Gopal
  • Joshuasingham at Aug 3, 2011 at 5:21 pm
    Hi Gopal,

    Can you elaborate further what you mean by IO size between iostats and
    filestat

    Thanks
    On Wednesday, August 3, 2011, K Gopalakrishnan wrote:
    IO size between iostats and filestat.

    -Gopal
    --
    http://www.freelists.org/webpage/oracle-l
  • Tanel Poder at Aug 3, 2011 at 7:23 pm
    Also - the Oracle wait events really measure system call completion times
    (plus some overhead) which include scheduling latency, filesystem overhead
    (posix single-writer locking if cio is not used etc), LVM translation
    overhead etc ... iostat measures at very low level (entry point to device
    drivers) - Oracle measures multiple layers higher ... plus the scheduling
    latency ...

    --
    Tanel Poder
    http://blog.tanelpoder.com
    On Wed, Aug 3, 2011 at 6:14 PM, K Gopalakrishnan wrote:

    IO size between iostats and filestat.

    -Gopal
    --
    http://www.freelists.org/webpage/oracle-l

    --
    http://www.freelists.org/webpage/oracle-l
  • Taylor, Chris David at Aug 3, 2011 at 3:24 pm
    Well, there's this for IBM zOS systems

    Document TitleAWR Report Shows Huge Numbers For Av/Rd (Doc ID 465106.1)

    https://supporthtml.oracle.com/ep/faces/secure/km/DocumentDisplay.jspx?id=465106.1&h=Y

    There's also this
    Document TitleAWR REPORTS INCORRECT IO STATS FOR TABLESPACES AND DATAFILES (Doc ID 827104.1)
    https://supporthtml.oracle.com/ep/faces/secure/km/DocumentDisplay.jspx?id=827104.1&h=Y

    Chris Taylor
    Sr. Oracle DBA
    Ingram Barge Company
    Nashville, TN 37205
    Office: 615-517-3355
    Cell: 615-663-1673
    Email: chris.taylor_at_ingrambarge.com

    CONFIDENTIALITY NOTICE: This e-mail and any attachments are confidential and may also be privileged. If you are not the named recipient, please notify the sender immediately and delete the contents of this message without disclosing the contents to anyone, using them for any purpose, or storing or copying the information on any medium.

    From: oracle-l-bounce_at_freelists.org On Behalf Of joshuasingham
    Sent: Wednesday, August 03, 2011 10:00 AM
    To: oracle-l@freelists.org
    Subject: iostat and awr File IO Stats difference

    Hi,

    I been looking at some (10.2.0.4) on AIX 64 bit Awr report File IO Stats and can see that the Av Rd(ms) for some of the files are consistently above 50 to 60 ms over a 15min interval but when I reported this storage guy he mention and sent me the Iostat to prove that the service time in the same timeline is average of 20ms for the disk involve . What can cause the difference between the AWR and iostat readings

    thanks

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postedAug 3, '11 at 2:59p
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