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Oracle Database 11g Performance Tuning Recipes: A Problem-Solution Approach by Bill Padfield, Darl Kuhn, Sam R. Alapati

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C H A P T E R  12

Execution Plan Optimization and Consistency

An execution plan describes how Oracle will retrieve the data to satisfy the results of a query. When you submit a SQL statement, the query optimizer quickly produces several execution plans and will determine which plan is most efficient. In most scenarios, the prior behavior results in a well-performing execution plan. However, you will encounter situations where you know additional details about your environment and need to adjust the optimizer's choice of an execution plan. Listed next are features you can use to influence the decision path the optimizer uses when selecting a plan:

  • Initialization parameters
  • Statistics
  • Hints
  • SQL profiles
  • SQL plan management (plan baselines)

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