RE: Usage of Baselines to prevent plan changes
Date: Wed, 28 Sep 2016 16:11:24 +0000
Message-ID: <VI1PR07MB1390ECB289B6BFF0912A5EC3A1CF0_at_VI1PR07MB1390.eurprd07.prod.outlook.com>
Part of the real power of baselines is the ability to evolve them and have one or more potential plans available to the optimizer, but only those which you allow.
There is a hard parse overhead (cost is parsed with no hints and then parsed again with hints to replicate the baseline) but unless you are really parse-heavy, you're not going to notice.
regards
Neil C
https://chandlerdba.wordpress.com/
Date: Wed, 28 Sep 2016 10:05:19 -0400
From: JBECKSTROM_at_gcrta.org<mailto:JBECKSTROM_at_gcrta.org> To: oracle-l_at_freelists.org<mailto:oracle-l_at_freelists.org>; oracle-db-l_at_Groups.ITtoolbox.com<mailto:oracle-db-l_at_Groups.ITtoolbox.com> Subject: Usage of Baselines to prevent plan changes
Over the past year, we have encountered problems where a SQL statement suddenly starts performing badly. In the past, we would either create a SQL Profile or alter the SQL with hints to get the old plan back. Just wondering if people used Baselines to prevent this form occurring and how well they work? This is an Oracle EBS system. If we use Baselines and Oracle changes the table structure adding an index to improve performance, would the new index be ignored because of the Baseline?
Jeffrey Beckstrom
Lead Database Administrator
Information Technology Department
Greater Cleveland Regional Transit Authority
1240 W. 6th Street
Cleveland, Ohio 44113
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Received on Wed Sep 28 2016 - 18:11:24 CEST