Integer 

Dynamic. Scope = ALTER SYSTEM. 

Operating system dependent, usually 2 

Any non-zero number 

Note: This parameter applies to parallel execution in exclusive mode as well as in the Oracle Parallel Server environment. 

PARALLEL_THREADS_PER_CPU specifies the default degree of parallelism for the instance and determines the parallel adaptive and load balancing algorithms. The parameter describes the number of parallel execution processes or "threads" that a CPU can handle during parallel execution.

The default is platform dependent and is adequate in most cases. You should decrease the value of this parameter if the machine appears to be overloaded when a representative parallel query is executed. You should increase the value if the system is I/O bound.

See Also: Oracle8i Designing and Tuning for Performance for more information on tuning parallel execution.