RE: CPU COSTING

From: Khedr, Waleed <Waleed.Khedr_at_FMR.COM>
Date: Fri, 23 Apr 2004 10:25:46 -0400
Message-ID: <42BBD772AC30EA428B057864E203C999113F47@MSGBOSCLF2WIN.DMN1.FMR.COM>

So for reads (i/o0 it measures the logical reads that might get = translated to physical or not. It's affected by the buffer cache, and = this makes sense.

So as you said, any changes/tuning to oica and oic (opt_ind_cache) might = need to be altered again.

Waleed

-----Original Message-----

From: Jonathan Lewis [mailto:jonathan_at_jlcomp.demon.co.uk] Sent: Friday, April 23, 2004 10:08 AM
To: oracle-l_at_freelists.org
Subject: Re: CPU COSTING

"CPU Costing" specifically estimates the CPU time=20 needed for all operations, so there is a 'CPUCycle count' for a logical I/O, a CPUCycle count for comparing locating a row in a block, a CPUCycle count for skipping over each column in a row to find the right one and so on.

Loosely, when CPUCosting is enabled it's part of enabling the CPU cost model, normally controlled by=20 parameter _optimizer_cost_model, which can be set to IO, CPU, or CHOOSE.

So in fact, the I/O costing changes at the same time, so that (in particular):

cost of t/s =3D blocks to scan / recorded MBRC *

                        mreadtim / sreadtim +=20
                        CPU cost.

I've got a paper coming out on OTN in a couple of weeks that talks about it a bit.

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

April 2004 Iceland http://www.index.is/oracleday.php=20 June 2004 UK - Optimising Oracle Seminar July 2004 USA West Coast, Optimising Oracle Seminar August 2004 Charlotte NC, Optimising Oracle Seminar September 2004 USA East Coast, Optimising Oracle Seminar September2004 UK - Optimising Oracle Seminar

Please see the official ORACLE-L FAQ: http://www.orafaq.com

To unsubscribe send email to: oracle-l-request_at_freelists.org put 'unsubscribe' in the subject line.

--
Archives are at http://www.freelists.org/archives/oracle-l/
FAQ is at http://www.freelists.org/help/fom-serve/cache/1.html


-----------------------------------------------------------------

Received on Fri Apr 23 2004 - 09:25:34 CDT