1.249 PARALLEL_DEGREE_POLICY

PARALLEL_DEGREE_POLICY specifies whether automatic degree of parallelism, statement queuing, and in-memory parallel execution will be enabled.

Property Description

Parameter type

String

Syntax

PARALLEL_DEGREE_POLICY = { MANUAL | LIMITED | AUTO | ADAPTIVE }

Default value

MANUAL

Modifiable

ALTER SESSION, ALTER SYSTEM

Modifiable in a PDB

Yes

Basic

No

Values

Note:

Automatic degree of parallelism will be enabled regardless of the value of PARALLEL_DEGREE_POLICY if a PARALLEL hint is used at the SQL statement level.

  • MANUAL

    Disables automatic degree of parallelism, statement queuing, and in-memory parallel execution. This reverts the behavior of parallel execution to what it was prior to Oracle Database 11g Release 2 (11.2). This is the default.

  • LIMITED

    Enables automatic degree of parallelism for some statements but statement queuing and in-memory Parallel Execution are disabled. Automatic degree of parallelism is only applied to those statements that access tables or indexes decorated explicitly with the DEFAULT degree of parallelism using the PARALLEL clause. Statements that do not access any tables or indexes decorated with the DEFAULT degree of parallelism will retain the MANUAL behavior.

  • AUTO

    Enables automatic degree of parallelism, statement queuing, and in-memory parallel execution.

  • ADAPTIVE

    This value enables automatic degree of parallelism, statement queuing and in-memory parallel execution, similar to the AUTO value. In addition, performance feedback is enabled. Performance feedback helps to improve the degree of parallelism automatically chosen for repeated SQL statements. After the initial execution of a statement, the degree of parallelism chosen by the optimizer is compared to the degree of parallelism computed based on the actual execution performance. If they vary significantly, then the statement is marked for re-parse and the initial execution performance statistics (for example, CPU-time) are provided as feedback for subsequent executions. The optimizer uses the initial execution performance statistics to better determine a degree of parallelism for subsequent executions.

See Also: