impdp did not run parallel

Hi friends,

on linux 8 and oracle 19c database

I run expdp dumpfile=xxx%u parallel=20 .....

and it did run ok with 20 files

I then test impdp dumpfile=xxx%u parallel=20

and I checked if 20 processes in the database and there is only 2.

SQL> select sid, serial#, program, module from v$session where module like 'Data%';

    SID  SERIAL# PROGRAM

---------- ---------- ------------------------------------------------

MODULE                             

----------------------------------------------------------------

    797   20157 oracle@xxx (DM00)

Data Pump Master                       

   1168   27875 oracle@xxx (DW00)

Data Pump Worker                         

Please advise what is going on?

Thanks and appreciated !

Friendly