PARALLEL_THREADS_PER_CPU

Parameter type	Integer
Default value	Operating system-dependent, usually 2
Parameter class	Dynamic: ALTER SYSTEM
Range of values	Any nonzero number

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.