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Re: T3's and forcedirectio questions

From: Connor McDonald <hamcdc_at_yahoo.co.uk>
Date: Fri, 19 Jul 2002 13:30:50 -0800
Message-ID: <F001.0049D155.20020719133050@fatcity.com>

  1. 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
  2. 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


Connor McDonald
http://www.oracledba.co.uk
http://www.oaktable.net

"Remember amateurs built the ark - Professionals built the Titanic"



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

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