Parallel execution doubles number of processes on AIX

Hi,

When I start parallel statement in database on AIX than number of sessions is twice as much as parallel degree .

for example: index rebuild parallel 8 is spawning 16 processes in v$session.

On Linux it does not occur ( degree 8 and 8 sessions visible )

. Could anyone explain to me why is that ?

AIX: 7.2 LPAR

DB 12.2

parallel_threads_per_cpu=1

parallel_servers_target=96

parallel_max_servers=240

parallel_degree_policy=MANUAL

parallel_degree_limit=CPU

Thanks