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OPTIMIZER_INDEX_COST_ADJ(转)

原创 Linux操作系统 作者:tochar 时间:2007-07-27 00:00:00 0 删除 编辑

OPTIMIZER_INDEX_COST_ADJ

Parameter type

Integer

Default value

100

Parameter class

Dynamic: ALTER SESSION

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.


Note:

The adjustment does not apply to user-defined cost functions for domain indexes.


See Also:

Oracle9i Database Performance Tuning Guide and Reference for more information on setting this parameter, and on its relationship to "OPTIMIZER_INDEX_CACHING"


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