Oracle® Database Reference 11g Release 2 (11.2) E40402-08 |
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Property | Description |
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Parameter type | Integer |
Default value | PARALLEL_THREADS_PER_CPU * CPU_COUNT * concurrent_parallel_users * 2 |
Modifiable | ALTER SYSTEM |
Range of values | 0 to PARALLEL_MAX_SERVERS |
Basic | No |
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 PARALLEL_SERVERS_TARGET
.
By default, 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 is dependent 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.