RE: db_file_multiblock_read_count causing full scans to take longer?

From: Christian Antognini <Christian.Antognini_at_trivadis.com>
Date: Tue, 19 Dec 2006 20:43:21 +0100
Message-ID: <F2C9CCA71510B442AF71446CAE8AEBAF8B57B9@MSXVS04.trivadis.com>

Don

> FWIW I did do 10046 traces of non-parallel full scans using various
> db_file_multiblock_read_count values, from 16, 32, 64, 128, and 256.
> 128 seemed to be where it topped out. However I'm finding the poor
> performance at anything over 32 now.

Be careful, the performance of non-parallel FTS is highly dependent on the blocks already stored in the buffer cache. In fact Oracle never reads a cached block...

Therefore, to find the best db_file_multiblock_read_count, it makes sense to flush the buffer cache before each FTS.

HTH
Chris

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Received on Tue Dec 19 2006 - 13:43:21 CST