From oracle-l-bounce@freelists.org Tue May 17 17:12:34 2005 Return-Path: Received: from air891.startdedicated.com (root@localhost) by orafaq.com (8.12.10/8.12.10) with ESMTP id j4HMCYuH020146 for ; Tue, 17 May 2005 17:12:34 -0500 X-ClientAddr: 206.53.239.180 Received: from turing.freelists.org (freelists-180.iquest.net [206.53.239.180]) by air891.startdedicated.com (8.12.10/8.12.10) with ESMTP id j4HMCY4Z020142 for ; Tue, 17 May 2005 17:12:34 -0500 Received: from localhost (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id 24644194644; Tue, 17 May 2005 16:09:45 -0500 (EST) Received: from turing.freelists.org ([127.0.0.1]) by localhost (turing [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 31684-06; Tue, 17 May 2005 16:09:44 -0500 (EST) Received: from turing (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id 7BC721940F2; Tue, 17 May 2005 16:09:44 -0500 (EST) Message-ID: <428A5D27.40908@centrexcc.com> Date: Tue, 17 May 2005 15:07:51 -0600 From: Wolfgang Breitling Organization: Centrex Consulting Corporation User-Agent: Mozilla Thunderbird 0.7.2 (Windows/20040707) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Christo Kutrovsky Cc: oracle-l Subject: Re: 10g System statistics - single and multi References: <52a152eb0505171232556f3711@mail.gmail.com> <428A57C7.7040002@centrexcc.com> <52a152eb05051713544f014099@mail.gmail.com> In-Reply-To: <52a152eb05051713544f014099@mail.gmail.com> Content-type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit X-UCIT-MailScanner-Information: Please contact IT Help Desk at (403) 220-5555 for more information X-UCIT-MailScanner: Found to be clean X-UCIT-MailScanner-From: breitliw@centrexcc.com X-archive-position: 19804 X-ecartis-version: Ecartis v1.0.0 Sender: oracle-l-bounce@freelists.org Errors-To: oracle-l-bounce@freelists.org X-original-sender: breitliw@centrexcc.com Precedence: normal Reply-To: breitliw@centrexcc.com X-list: oracle-l X-Virus-Scanned: by amavisd-new-20030616-p9 (Debian) at avenirtech.net X-Spam-Level: X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on air891.startdedicated.com X-Spam-Status: No, hits=0.0 required=5.0 tests=AWL autolearn=ham version=2.63 Christo, I don't know how you come to that conclusion. The value of MBRC does not factor into the decision whether to use the new cost formula or not. It is mreadtm which needs to be greater than sreadtm for the new cost formula (and cpu costing, at least in 9i) to be used. Only then does the MBRC value factor in. And I just realized that it misquoted the cost for a FTS under the new flrmula. It is of course cost(FTS) = #blocks/MBRC * MREADTM / SREADTM I suppose the optimizer developers chose to ignore the system statistics if they look suspicious and from their point of view mreadtm has to be greater than sreadtm and if it is not they ignore the entire thing. Of course, that could change at any time. Until then you need to check the values of your gathered system statistics for mreadtm > sreadtm. Christo Kutrovsky wrote: > Yes, this is exactly my observation. I dont understand why Oracle did > this ! They will never have this right, it seems. > > actually, i tried mread = 1.00000001 and sread = 1 -> cost = ~650 > > So basically, this makes using a very high value for mbrc (so that > your mread > sread) almost mandatory in 10g, otherwise your FTS costs > would use the old formula. > > -- Regards Wolfgang Breitling Centrex Consulting Corporation www.centrexcc.com -- http://www.freelists.org/webpage/oracle-l