RE: db_file_multiblock_read_count and performance

  • From: "Post, Ethan" <Ethan.Post@xxxxxx>
  • To: "Jared Still" <jkstill@xxxxxxxxx>
  • Date: Tue, 7 Dec 2004 13:19:19 -0600

> 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optimizer_index_cost_adj is no longer valid because IO bandwidth may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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