Title: RE: db_file_multiblock_read_count/max i/o

thanks Connor.  Excellent info.

Lisa Koivu
Ft. Lauderdale, FL, USA

    -----Original Message-----
    From:   Connor McDonald [SMTP:[EMAIL PROTECTED]]
    Sent:   Monday, June 25, 2001 2:18 PM
    To:     Multiple recipients of list ORACLE-L
    Subject:        RE: db_file_multiblock_read_count/max i/o

    alter session set db_file_multiblock_read_count =
    32768;

    enable event 10046 at level 8

    do a large full scan

    check the trace file, 'p3' tells you the max mb count
    it could use, and thus the max io (from oracle's
    perspective)

    hth
    connor

    --- "Koivu, Lisa" <[EMAIL PROTECTED]> wrote: >
    Um....   that was something I relied upon my trusty
    > SA to tell me. 
    > I can't answer that.  Sorry.  Anyone know?  I do
    > know how to determine this
    > is different between platforms. 
    >
    > Lisa
    >
    > > -----Original Message-----
    > > From:       Smith, Ron L. [SMTP:[EMAIL PROTECTED]]
    > > Sent:       Monday, June 25, 2001 11:12 AM
    > > To: Multiple recipients of list ORACLE-L
    > > Subject:    RE: db_file_multiblock_read_count
    > >
    > > How do you tell for sure what the max i/o size is
    > set to?
    > >
    > > -----Original Message-----
    > > Sent: Monday, June 25, 2001 9:23 AM
    > > To: Multiple recipients of list ORACLE-L
    > >
    > >
    > >
    > > Hi Liam,
    > >
    > > 1.  Setting db_file_multiblock_count to a number
    > that when multiplied by
    > > your block size is greater than your max i/o size
    > on your host will
    > > encourage full table scans.  I also read somewhere
    > else about the effects
    > > of
    > > doing this, I know there's more to it than what
    > I've stated, but I don't
    > > remember off the top of my head (pre-coffee and
    > post-run this am)
    > >
    > > 2.  vmstat - look at the two columns that start
    > with pg.  Read the man
    > > page
    > > and it will explain it to you in detail. Also,
    > when you use vmstat be sure
    > > to give it an interval (like vmstat 2 10 - this
    > means display stats once
    > > every 2 seconds for a duration of 10 seconds).
    > The first line returned by
    > > vmstat will always be garbage (same with iostat).
    > >
    > > HTH
    > > Lisa Koivu
    > > Petite Clumsy Ninja-ette
    > > Ft. Lauderdale, FL, USA
    > >
    > >     -----Original Message-----
    > > Sent:   Monday, June 25, 2001 8:36 AM
    > > To:     Multiple recipients of list ORACLE-L
    > >
    > >     Listers,
    > >
    > >     I am attempting to tune a 7.3.4 OLTP database and
    > I have a couple of
    > >
    > > questions.
    > >
    > >     1. The db_file_multiblock_count is 64 which seems
    > way too high to
    > > me. What
    > > are the consequences, if any, of setting this
    > parameter too high?
    > >
    > >     2. I want to increase the SGA to be 20% of the
    > available memory
    > > (currently
    > > about 10%). Once I've made the change how can I
    > tell if the Unix machine
    > > is
    > > paging memory without a fancy GUI tool?
    > >
    > >     Many thanks in advance,
    > > Liam
    > >
    >
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    > > Author: Liam Morrin
    > >   INET: [EMAIL PROTECTED]
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    =====
    Connor McDonald
    http://www.oracledba.co.uk (mirrored at
    http://www.oradba.freeserve.co.uk)

    "Some days you're the pigeon, some days you're the statue"

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