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Home -> Community -> Mailing Lists -> Oracle-L -> Re: T3's and forcedirectio questions

Re: T3's and forcedirectio questions

From: Anjo Kolk <anjo_at_oraperf.com>
Date: Fri, 19 Jul 2002 14:43:18 -0800
Message-ID: <F001.0049D1C1.20020719144318@fatcity.com>


I think it is 2-4 * bs *mbr.

Anjo.

> Oracle (in class materials) recommends
> stripe size = block_size * multiblock_read_count.
> For example, if stripe size = 64k and block_size = 8k, then
> multiblock_read_count should be 8.
>
> Dennis Williams
> DBA
> Lifetouch, Inc.
> dwilliams_at_lifetouch.com
>
> -----Original Message-----
> Sent: Friday, July 19, 2002 4:31 PM
> To: Multiple recipients of list ORACLE-L
>
>
> a) multi block read count - its good to set it high to
> get the benefit from fts when they occur, but you also
> have to give oracle 'good' information. eg look at
> the optimizer_... parms to tell oracle more
> information about how good index caching is, and the
> difference between the cost of the multiblock read and
> a single block read (which in 8i oracle assumes to be
> equal). In 9i, using system level stats helps this
> considerably. Also, ensure that you are actually
> getting the full 1m (typically you wont on file
> systems unless you've tweaked them on creation). Some
> info at http://www.oracledba.co.uk/tips/mbrc.htm
>
> b) direct IO - if you turn this one, then you have
> freed up a chunk of memory from the file cache - which
> means you may need to then allocate this to oracle (by
> increasing the size of the buffer cache accordingly).
> The theory is that the oracle cache is 'smarter' than
> the unix cache because it respects things like extent
> boundaries etc etc
>
> hth
> connor
>
> --- Dave Morgan <dvmrgn_at_telusplanet.net> wrote: > Hi
> All,
> > I am attempting to improve performance in a shop
> > that
> > uses alot of T3 Storedge arrays to hold the oracle
> > datafiles.
> > I have already moved the redo logs onto to JBOD and
> > tweaked
> > ac couple other settings to make everyone happy but
> > I still
> > have some questions.
> >
> > 1. SUN best practises says set
> > db_multiblock_read_count to
> > a value that with the db block size equals 1M. This
> > forces
> > many foolish full table scans. I have fixed this by
> > knocking
> > the parameter down so the db does reads of 64kK but
> > does anyone
> > know if I can set the optimizer_index_* parameters
> > (and to what values)
> > so that I can set db_multiblock_read_count to match
> > the arrays
> > logical I/O setting?
> >
> > 2 Both Oracle and SUN recommend mounting the arrays
> > with
> > the forcedirectio option and then setting the oracle
> > _filesystemio_options to setall. This causes a 50%
> > performance
> > hit measured by timing representative jobs. Does
> > anyone know
> > why? Even Steve Adams recommends these settings yet
> > the numbers don't
> > lie.
> >
> > A grabbag of other stuff since I can't post to the
> > list from work.
> >
> > Thanks Kirti, for the answer to my listener question
> > a couple
> > of weeks ago
> >
> > Rachel, I have been running Linux/Oracle in
> > production since 8.1.6.
> > I hate to be a paranoid command line hack again but
> > the distribution
> > is irrelevant, Either understand linux, ie compile
> > your own kernels
> > and understand the system libraries, or get a
> > sysadmin who does. Trying
> > to keep up to certified combinations is hard enough
> > for commercial
> > UNIXes,
> > for linux it's easier just to roll your own. So what
> > if Oracle doesn't
> > formally support it. This list will ;)
> >
> > 40% higher throughput than the same box running
> > Oracle under Windblows,
> > 30% less administrative work.
> >
> > Upgrading the OCP. No-one cares what version of the
> > OCP you have. I took
> > mine at 7.3.4 and since then all anyone has asked is
> > do you have it. The
> > only
> > real value I found is it is helpful when applying
> > for a TN visa to work
> > in
> > the US.
> >
> > my $0.013, otherwise known as $CAN 0.02
> >
> >
> > Dave
> >
> > --
> > Dave Morgan
> > dvmrgn_at_telusplanet.net
> > 403 399 2442
> > --
> > Please see the official ORACLE-L FAQ:
> > http://www.orafaq.com
> > --
> > Author: Dave Morgan
> > INET: dvmrgn_at_telusplanet.net
> >
> > Fat City Network Services -- (858) 538-5051 FAX:
> > (858) 538-5051
> > San Diego, California -- Public Internet
> > access / Mailing Lists
> >
> --------------------------------------------------------------------
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> > also send the HELP command for other information
> > (like subscribing).
>
> =====
> Connor McDonald
> http://www.oracledba.co.uk
> http://www.oaktable.net
>
> "Remember amateurs built the ark - Professionals built the Titanic"
>
> __________________________________________________
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> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: =?iso-8859-1?q?Connor=20McDonald?=
> INET: hamcdc_at_yahoo.co.uk
>
> Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
> San Diego, California -- Public Internet access / Mailing Lists
> --------------------------------------------------------------------
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> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: DENNIS WILLIAMS
> INET: DWILLIAMS_at_LIFETOUCH.COM
>
> Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
> San Diego, California -- Public Internet access / Mailing Lists
> --------------------------------------------------------------------
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Anjo Kolk
  INET: anjo_at_oraperf.com

Fat City Network Services    -- (858) 538-5051  FAX: (858) 538-5051
San Diego, California        -- Public Internet access / Mailing Lists
--------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from).  You may
also send the HELP command for other information (like subscribing).
Received on Fri Jul 19 2002 - 17:43:18 CDT

Original text of this message

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