Parallel_automatic_tuning increase processes

Question

In my 8174 db (enterprise ed) on aix 51 with 4 cpu, i see processes parameter value equal to 192. But in my init , i set it to 20. I changed the value to 30 but show parameter/select from v$parameter it's always 192.
It's the case since i set parallel_automatic_tuning to true. When i set this parm to false, processes is what i expect.
Is it a normal behavior ?
Why process is set to 192 with my 4-cpu server ?

Answer 1

I found a formula but almost right :
processes will be set to the larger of :
- parallel_max_servers + 11 (bg process) + cpu_count x 4
- //max_servers x 1,2
and //max_servers should be equal to cpu x 2 x 5 = 40.
As my //max servers = 160, 160 x 1,2=192.
It's finally amost ok for me (with oracle formula, my //max servers should be = 40, not 160).