This parameter describes the number of parallel execution processes or threads that a CPU can handle during parallel execution.
It is used to:
The default is platform-dependent and is adequate in most cases (two on most platforms).
By default, Oracle will spawn two parallel server processes per each core on most systems.
gerardnico@orcl>show parameter PARALLEL_THREADS_PER_CPU
NAME TYPE VALUE
------------------------------------ ----------- ---------
parallel_threads_per_cpu integer 2