I think there is some confusion here.
System Manager is the configuration tool that connects only to 7-mode filers or cDOT cluster, not to OCUM.
OCUM is a management tool that mostly monitors your NetApp filers, but you don't use it to do configuration tasks.
System Manager handles both 7-mode and cDOT filers/clusters
OCUM has to be installed for one or another flavor. If your infrastructure has both 7-mode and cDOT systems installed, you should have two distincts installations of OCUM.