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 AI Database SQL Tuning Guide for information about adaptive plans