About

This parameter determines the maximum number of parallel servers that may be started for a database instance, should there be demand for them.

The default value on Oracle Database 10g and higher is:

<MATH> \text{PARALLEL MAX SERVERS} = 10 * \text{cpu count} * \text{parallels threads per cpu} </MATH>

where:

• Oracle Database - CPU_COUNT parameter
• Oracle Database - PARALLEL_THREADS_PER_CPU Parameter

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Rule of thumb

A good rule of thumb is to ensure parallel_max_servers is set to a number greater than : <MATH> \text{parallel_max_servers} > \text{maximum number of concurrent queries} * \text{maximum degree of parallelism need by a query} </MATH> where:

• degree of parallelism
• concurrent queries

By doing this you will ensure every query gets the appropriate number of parallel servers.

Documentation / Reference

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