"adop phase=apply patches=20128107" failed with error "admin server is down. Cannot proceed further"

Hi,

  We are upgrading ebs from 12.1.3 to 12.2.4 (DB already 11.2.0.4), and we finished application of 12.2.0 driver. Now we are at "Enabling Online Patching"=>Note 1531121.1=>Apply patch 20128107:R12.AD.C.

  When we try to apply patch 20128107:R12.AD.C with command:

adop phase=apply patches=20128107

we get following error :

***** W A R N I N G *****
ADMIN SERVER is down. Cannot proceed further...
Please start the ADMIN SERVER.


adop exiting with status = 3 (Fail)

Is it mandatory to have admin server up ? (We read in documentation that system should not be started).

Regards