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

1.239 PARALLEL_SERVERS_TARGET

PARALLEL_SERVERS_TARGET specifies the number of parallel server processes allowed to run parallel statements before statement queuing will be used.

Property Description

Parameter type

Integer

Default value

For a CDB:

Equal to the PARALLEL_MAX_SERVERS value for the CDB.

For a PDB or non-CDB:

PARALLEL_THREADS_PER_CPU * CPU_COUNT * concurrent_parallel_users * 2

Modifiable

ALTER SYSTEM

Modifiable in a PDB

No

Range of values

0 to PARALLEL_MAX_SERVERS

Basic

No

When the parameter PARALLEL_DEGREE_POLICY is set to ADAPTIVE or AUTO, Oracle will queue SQL statements that require parallel execution, if the necessary parallel server processes are not available. In a single instance database, statement queuing will begin once the number of parallel server processes active on the system is equal to or greater than PARALLEL_SERVERS_TARGET. In an Oracle RAC database, a statement running on one instance can allocate parallel server processes on another instance when necessary. For example, if a statement running on one instance requires parallel execution, but the number of parallel server processes active on that instance is equal to or greater than the value of PARALLEL_SERVERS_TARGET for that instance, then the statement can allocate parallel server processes on a different instance. Therefore, statement queuing in an Oracle RAC database will begin only when every instance has reached its PARALLEL_SERVER_TARGET threshold.

Note:

Consumer groups that have been marked with the PARALLEL_STMT_CRITICAL directive are allowed to bypass the parallel statement queue, and therefore may drive the total number of active parallel server processes beyond 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 depends on the memory initialization parameter settings for the instance. For example, if the MEMORY_TARGET or SGA_TARGET initialization parameter is set, then the number of concurrent_parallel_users = 4. If neither MEMORY_TARGET or SGA_TARGET is set, then PGA_AGGREGATE_TARGET is examined. If a value is set for PGA_AGGREGATE_TARGET, then concurrent_parallel_users = 2. If a value is not set for PGA_AGGREGATE_TARGET, then concurrent_parallel_users = 1.

Note that all serial (non-parallel) statements will execute immediately even if statement queuing has been activated.

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