1. Database Reference
  2. Initialization Parameters
  3. Initialization Parameters
  4. OPTIMIZER_ADAPTIVE_STATISTICS

2.242 OPTIMIZER_ADAPTIVE_STATISTICS

OPTIMIZER_ADAPTIVE_STATISTICS controls adaptive statistics. Some query shapes are too complex to rely on base table statistics alone, so the optimizer augments these statistics with adaptive statistics.

Property Description

Parameter type

Boolean

Default value

false

Modifiable

ALTER SESSION, ALTER SYSTEM

Modifiable in a PDB

Yes

Range of values

true | false

Basic

No

Oracle RAC

The same value must be set on all instances

Setting this parameter to false disables the following adaptive features:

  • SQL plan directives

  • Statistics feedback for joins

  • Adaptive dynamic sampling for parallel execution

Note:

Setting OPTIMIZER_ADAPTIVE_STATISTICS to false preserves the statistics feedback functionality that was introduced in Oracle Database 11g.

OPTIMIZER_ADAPTIVE_STATISTICS does not control the creation of SQL plan directives. SQL plan directives will be created even if this parameter is false, but they will not be used to refine SQL execution plans with dynamic sampling.

See Also:

Oracle Database SQL Tuning Guide for information about adaptive plans