This parameter determines the number of parallel servers that will be started during database startup.
By default the value is 0.
It is recommended that you set parallel_min_servers to:
This will ensure that there are ample parallel server processes available for the majority of the queries executed on the system and queries will not suffer any additional overhead of having to spawn extra parallel servers.
However, if extra parallel servers are required for additional queries above you average workload they can be spawn “on the fly” up to the value of parallel_max_servers.
Any additional parallel server processes that are spawned above parallel_min_servers will be killed after they have been inactive for a certain about of time and will have to be re-spawned if they are need again in the future.