From oracle-l-bounce@freelists.org Mon May 9 12:18:27 2005 Return-Path: Received: from air891.startdedicated.com (root@localhost) by orafaq.com (8.12.10/8.12.10) with ESMTP id j49HIQC4023248 for ; Mon, 9 May 2005 12:18:26 -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 j49HIQ4Z023244 for ; Mon, 9 May 2005 12:18:26 -0500 Received: from localhost (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id 1EBF0191636; Mon, 9 May 2005 11:15:46 -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 06218-04; Mon, 9 May 2005 11:15:46 -0500 (EST) Received: from turing (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id A107F19167E; Mon, 9 May 2005 11:15:45 -0500 (EST) X-MimeOLE: Produced By Microsoft Exchange V6.0.6487.1 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Subject: RE: Optimizer change from 8i-9i Date: Mon, 9 May 2005 18:13:55 +0200 Message-ID: <7F0C000A3ABA6241A10C9ABF37EEB46D04081D@MSXVS01.trivadis.com> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: Optimizer change from 8i-9i Thread-Index: AcVUe8jzA+e17aawRsqctSkZtocCXAANc3ug From: "Christian Antognini" To: Cc: X-archive-position: 19455 X-ecartis-version: Ecartis v1.0.0 Sender: oracle-l-bounce@freelists.org Errors-To: oracle-l-bounce@freelists.org X-original-sender: Christian.Antognini@trivadis.com Precedence: normal Reply-To: Christian.Antognini@trivadis.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 Hi Zhu >1. For SQLs using RBO, the plan for the existing SQL won''t change, >right? As oracle says no change for RBO since oracle 7.3. Wrong. You could see some differences. (they are lying to us!) >2. For SQLs using CBO(as some feature will force CBO parsee), when the >optimizer_feature_enabled=3D3D817, and don't change any = optimizer_related >parameters, is it still possible for SQL to choose different plan in >9i as the old plan in 8i? (Maybe because of different Cost caculation >in 9i?) Also in this case you could have different execution plans.=20 IMHO the only way to guarantee a good migration from 8i to 9i is to = completely reconfigure the CBO and do some extended performance tests. = (I was called by more than one customer when it was too late!!!!) HTH Chris -- http://www.freelists.org/webpage/oracle-l