Cost Based Optimizer
From Oracle FAQ
The Cost Based Optimizer (CBO) is a SQL Query optimizer that uses data statistics to identify the query plan with lowest cost before execution. The cost is based on the number of rows in a table, index efficiency, etc.
All applications should be converted to use the Cost Based Optimizer as the Rule Based Optimizer is not be supported in Oracle 10g and above releases.
- DBMS_STATS - PL/SQL package used to gather optimizer stats
- Rule Based Optimizer
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