Oracle Parameter optimizer_index_cost_adj Performance


From Oracle Documentation,

Default value 100
Modifiable ALTER SESSION, ALTER SYSTEM
Range of values 1 to 10000

OPTIMIZER_INDEX_COST_ADJ lets you tune optimizer behavior for access path selection to be more or less index friendly—that is, to make the optimizer more or less prone to selecting an index access path over a full table scan.

The default for this parameter is 100 percent, at which the optimizer evaluates index access paths at the regular cost. Any other value makes the optimizer evaluate the access path at that percentage of the regular cost. For example, a setting of 50 makes the index access path look half as expensive as normal.

The default value 100 and 0 for OPTIMIZER_INDEX_COST_ADJ and OPTIMIZER_INDEX_CACHING respectively are set for Data Warehouse System.

For OLTP system, setting 10 to OPTIMIZER_INDEX_COST_ADJ and 90 to OPTIMIZER_INDEX_CACHING will perform good result.

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