Optimizer features enabled

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he optimizer_features_enable parameter shifts the behavior of the optimizer backwards to the specified release. The optimizer_features_enable is very useful when an execution plan changes after the application of a patch or the installation of a new release. You can set optimizer_features_enable at the system level (as an init.ora parameter), at the session level, and at the SQL statement level (as a hint, see below):

  • SYSTEM = optimizer_features_enable='11.2.0.3'
  • SESSION = alter session set optimizer_features_enable='11.2.0.3';
  • SQL = select /*+ optimizer_features_enable('9.2.0') */