The OPC$-logicals control the function of OPCOM.

  OPC$OPA0_ENABLE         enable OPA0:
                          (documented in SYS$MANAGER:SYLOGICALS.COM)
  OPC$OPA0_CLASSES        classes to enable OPA0: for
                          (documented in SYS$MANAGER:SYLOGICALS.COM)
  OPC$LOGFILE_ENABLE      enable logfile
                          (documented in SYS$MANAGER:SYLOGICALS.COM)
  OPC$LOGFILE_CLASSES     classes to enable logfile for
                          (documented in SYS$MANAGER:SYLOGICALS.COM)
  OPC$LOGFILE_NAME        name of logfile
                          (documented in SYS$MANAGER:SYLOGICALS.COM)
  OPC$ACK                 request ACK from al cluster members
  OPC$DUMP_MAILBOX        dump mailbox content to logfile
  OPC$INCREASE_STRESS     increase OPCOM traffic artificially
  OPC$UNLOAD              used by SYS$SYSTEM:SHUTDOWN.COM
  OPC$REBOOT              used by SYS$SYSTEM:SHUTDOWN.COM
  OPC$NODUMP              used by SYS$SYSTEM:SHUTDOWN.COM
  OPC$CLUSTER_SHUTDOWN    used by SYS$SYSTEM:SHUTDOWN.COM
  OPC$REMOVE_NODE         used by SYS$SYSTEM:SHUTDOWN.COM
  OPC$DEBUG_FILE          write debug information to file
  OPC$DEBUG_TERMINAL      write debug information to terminal