From oracle-l-bounce@freelists.org Thu Aug 19 09:38:35 2004 Return-Path: Received: from air189.startdedicated.com (root@localhost) by orafaq.com (8.11.6/8.11.6) with ESMTP id i7JEcZe16430 for ; Thu, 19 Aug 2004 09:38:35 -0500 X-ClientAddr: 206.53.239.180 Received: from turing.freelists.org (freelists-180.iquest.net [206.53.239.180]) by air189.startdedicated.com (8.11.6/8.11.6) with ESMTP id i7JEcYI16416 for ; Thu, 19 Aug 2004 09:38:35 -0500 Received: from localhost (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id BAD3072CA64; Thu, 19 Aug 2004 09:37:20 -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 01220-90; Thu, 19 Aug 2004 09:37:20 -0500 (EST) Received: from turing (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id 165BF72CA5E; Thu, 19 Aug 2004 09:37:20 -0500 (EST) Received: with ECARTIS (v1.0.0; list oracle-l); Thu, 19 Aug 2004 09:35:55 -0500 (EST) X-Original-To: oracle-l@freelists.org Delivered-To: oracle-l@freelists.org Received: from localhost (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id 52A9572C9AF for ; Thu, 19 Aug 2004 09:35:55 -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 01058-84 for ; Thu, 19 Aug 2004 09:35:55 -0500 (EST) Received: from imcsvr-2.aetvn.com (imcsvr-2.aetvn.com [216.89.67.159]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id 62D0D72C9AA for ; Thu, 19 Aug 2004 09:35:54 -0500 (EST) Received: by imcsvr-2.aetvn.com with Internet Mail Service (5.5.2653.19) id ; Thu, 19 Aug 2004 10:36:52 -0400 Message-ID: <30462D80AA52E74698512ADCC4F7EAA31223967D@exchange.aetvn.com> From: "Gogala, Mladen" To: "'oracle-l@freelists.org'" Subject: RE: db_file_mutliblock_read_count and physical IO Date: Thu, 19 Aug 2004 10:36:24 -0400 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2653.19) Content-type: text/plain X-Virus-Scanned: by amavisd-new at freelists.org Content-Transfer-Encoding: 8bit X-archive-position: 7884 X-ecartis-version: Ecartis v1.0.0 Sender: oracle-l-bounce@freelists.org Errors-To: oracle-l-bounce@freelists.org X-original-sender: Mladen.Gogala@aetn.com Precedence: normal Reply-To: oracle-l@freelists.org X-list: oracle-l X-Virus-Scanned: by amavisd-new at freelists.org I find that the most confusion is caused by "direct read/write" events because they're caused not only by sorts but also by PQ processes which read directly from the file into PGA, bypassing the buffer cache. People have been quick to establish new myths, which tell us that "scattered I/O = full table scan, sequential disk read = index read". Direct I/O is perplexing, if you happen to be a believer. -- Mladen Gogala Oracle DBA email:mladeng@aetvn.com Ext: 9787 > -----Original Message----- > From: Cary Millsap [mailto:cary.millsap@hotsos.com] > Sent: Thursday, August 19, 2004 10:28 AM > To: oracle-l@freelists.org > Subject: RE: db_file_mutliblock_read_count and physical IO > My concern is that people who have learned ridiculous > nonsense like the "80/20 rule of indexing" and that "Oracle > reads records from disk into = RAM" might also not understand > that the blocks being read can be from = segments of > different types. In particular, I find people to be somewhat > surprised = on occasion when they see an undo block being > read via one of the kernel's = read events. ---------------------------------------------------------------- Please see the official ORACLE-L FAQ: http://www.orafaq.com ---------------------------------------------------------------- To unsubscribe send email to: oracle-l-request@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 -----------------------------------------------------------------