VMS Help DECnet-Plus, DCL Commands, SET, HOST, /MOP, Parameter  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    CLIENT

       Specifies the name of the MOP CLIENT entity which describes
       the remote system that is the target of the console carrier
       request.  This is an optional parameter.  If omitted, you
       must specify the /CIRCUIT and /ADDRESS qualifiers.