- 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
- 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
>
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Connor McDonald
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Received on Fri Jul 19 2002 - 16:30:50 CDT
