Oracle Database - PARALLEL_THREADS_PER_CPU Parameter

This parameter describes the number of parallel execution processes or threads that a CPU can handle during parallel execution.

It is used to:

• calculate the default degree of parallelism for the instance
• and determines the maximum number of parallel servers if parallel_max_servers is not set.

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

• Oracle SQL Parallel Execution - An Oracle White Paper - June 2008