Re: optimizer settings

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Tue, 2 Mar 2004 08:10:56 -0000
Message-ID: <002f01c4002d$e3f9be20$6702a8c0@Primary>

That was the interpretation that Tim Gorman supplied as a nice 'human' way of looking at it. Since it still works in 9i, you could (for values up to 100) view it as the fraction of single block visits that are likely to turn into disk read requests. Then the sreadtim is a number that tells you how long each of the reads takes.

Regards

Jonathan Lewis
http://www.jlcomp.demon.co.uk

The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html

March 2004 Hotsos Symposium - The Burden of Proof Dynamic Sampling - an investigation
March 2004 Charlotte OUG (www.cltoug.org) CBO Tutorial April 2004 Iceland
June 2004 UK - Optimising Oracle Seminar

Original Message ----- From: "Lim, Binley" <Binley.Lim_at_NBNZ.CO.NZ> To: <oracle-l_at_freelists.org> Sent: Monday, March 01, 2004 11:12 PM Subject: RE: optimizer settings

>
> I thought CPU costing is supposed to do that for you, without having to
> tweak O_I_C_A yourself...?
>
> > -----Original Message-----
> > From: K Gopalakrishnan [SMTP:kaygopal_at_yahoo.com]
> > Sent: Tuesday, March 02, 2004 3:58 AM
> > To: oracle-l_at_freelists.org
> > Subject: Re: optimizer settings
> >
> > Jaffar:
> >
> > They are the default settings on 9i. You may not need to tweak the max
> > permutations
> > unless you have more than 7-8 tables in where condition. However you can
> > reduce the
> > optimizer_index_cost _adj after some analysis on single block read to
> > multiblock read
> > timings. You can find 'Search for Intelligence in CBO' paper by Tim
Gorman
> > in his
> > site www.evdbt.com

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Received on Tue Mar 02 2004 - 02:07:45 CST