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RE: db_file_multiblock_read_count and performance

From: Post, Ethan <Ethan.Post_at_ps.net>
Date: Tue, 7 Dec 2004 13:19:19 -0600
Message-ID: <83FCA77436D6A14883E132C63F4101D001DCCC25@pscdalpexch50.perotsystems.net>


> On my linux box at work the 'ideal' would be 128. Keep in mind
> that the value of DBFMBRC will influence the CBO. You may
> find it favoring FTS more often than you would like.

I would think ideal is "as fast as possible" and assuming you tell Oracle the truth about speed of multiblock reads verse single block with optimizer_index_cost_adj everything should work out fine, even if full scans are favored. Of course too many scans at the same time and optimizer_index_cost_adj is no longer valid because IO bandwidth may effect response times, so I guess this is where system stats has a supreme advantage.=20

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Received on Tue Dec 07 2004 - 13:24:39 CST

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