Return-Path: Received: from ensim.rackshack.net (root@localhost) by orafaq.net (8.11.6/8.11.6) with ESMTP id h6UKwrB21929 for ; Wed, 30 Jul 2003 15:58:53 -0500 X-ClientAddr: 66.27.56.210 Received: from ns3.fatcity.com (rrcs-west-66-27-56-210.biz.rr.com [66.27.56.210]) by ensim.rackshack.net (8.11.6/8.11.6) with ESMTP id h6UKwrp21923 for ; Wed, 30 Jul 2003 15:58:53 -0500 Received: from ns3.fatcity.com (localhost.localdomain [127.0.0.1]) by ns3.fatcity.com (8.12.5/8.12.5) with ESMTP id h6UIKLPM000861 for ; Wed, 30 Jul 2003 11:25:38 -0700 Received: (from root@localhost) by ns3.fatcity.com (8.12.5/8.12.5/Submit) id h6UGaR8v010755 for oracle-l@orafaq.net; Wed, 30 Jul 2003 09:36:27 -0700 Received: by fatcity.com (05-Jun-2003/v1.0g-b73/bab) via fatcity.com id 005C7DB7; Wed, 30 Jul 2003 09:24:48 -0800 Message-ID: Date: Wed, 30 Jul 2003 09:24:48 -0800 To: Multiple recipients of list ORACLE-L X-Comment: Oracle RDBMS Community Forum X-Sender: Wolfgang Breitling Sender: ml-errors@fatcity.com Reply-To: ORACLE-L@fatcity.com Errors-To: ML-ERRORS@fatcity.com From: Wolfgang Breitling Subject: Re: optimizer parameters in Oracle 9.2 Organization: Fat City Network Services, San Diego, California X-ListServer: v1.0g, build 73; ListGuru (c) 1996-2003 Bruce A. Bergman Precedence: bulk Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed Content-Transfer-Encoding: 7bit Collecting system statistics in 9i is supposed to automagically do what optimizer_index_cost_adj does, at least if you set it according to the formula in Tim's paper ("The Search for Intelligent Life in the Cost-Based Optimizer"). The CBO then uses different cost factors for single-block IO (predominantly index accesses) and multiblock IO (table and index scans). At 06:04 AM 7/30/2003 -0800, you wrote: >Hi all: > >I have been reading on the optimizer_ parameters for >Oracle 9i - optimizer_max_permutation, >optimizer_index_caching and optimizer_index_cost_adj. >I have also been playing whith them and I can see that >they affect the explain plans for some queries quite >dramatically. Is there any guidelines for what they >should be set to for optimum performance (some kind of >range and may be relationship between the values) or >is this mostly a trial and error kind of thing? I have >seen a few discussion on the Oracle Metalink, but >mostly they are very specific - try this value or try >that value. Does anyone have a link to a document with >something more systematic than that? Wolfgang Breitling Oracle7, 8, 8i, 9i OCP DBA Centrex Consulting Corporation http://www.centrexcc.com -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Wolfgang Breitling INET: breitliw@centrexcc.com Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru@fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).