Upgrading From Oracle Database 9i to 10g: What to Expect From the Optimizer

Overview

Since its introduction in Oracle 7.0, people have been fascinated and intimidated by the Cost-Based Optimizer (CBO) and the statistics that feed it. It has long been felt that the internals of the CBO were shrouded in mystery and that a degree in wizardry was needed to work with it. One of the most daunting activities a DBA can therefore undertake is upgrading the database to a new version. Having to comprehend all of the new features and to deal with potential plan changes can be overwhelming. This paper aims to dispel the mystery by explaining in detail what to expect from the CBO when one upgrade from Oracle database 9i to 10g.