|Oracle® Database Reference
12c Release 1 (12.1)
|PDF · Mobi · ePub|
|Range of values||
PARALLEL_SERVERS_TARGET specifies the number of parallel server processes allowed to run parallel statements before statement queuing will be used. When the parameter
PARALLEL_DEGREE_POLICY is set to
AUTO, Oracle will queue SQL statements that require parallel execution, if the necessary parallel server processes are not available. Statement queuing will begin once the number of parallel server processes active on the system is equal to or greater than
Note:Consumer groups that have been marked with the
PARALLEL_STMT_CRITICALdirective are allowed to bypass the parallel statement queue, and therefore may drive the total number of active parallel server processes beyond
PARALLEL_SERVERS_TARGET is set lower than the maximum number of parallel server processes allowed on the system (
PARALLEL_MAX_SERVERS) to ensure each parallel statement will get all of the parallel server resources required and to prevent overloading the system with parallel server processes.
The number of concurrent parallel users running at default degree of parallelism on an instance depends on the memory management setting. If automatic memory management is disabled (manual mode), then the number of concurrent parallel users is 1. If PGA automatic memory management is enabled, the number of concurrent parallel users is 2. If global memory management or SGA memory target is used in addition to PGA automatic memory management, then the number of concurrent parallel users is 4.
Note that all serial (non-parallel) statements will execute immediately even if statement queuing has been activated.
See Also:Oracle Database VLDB and Partitioning Guide for more information about this parameter