VMS Help SET, DISPLAY, Qualifiers, /SERVER  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /SERVER=server-number

    Defines the server to be associated with the display device
    indicated by the display-device parameter to the SET DEVICE
    command. Using the transport mechanism, the server passes
    data between the user and the application. In some hardware
    configurations, the system supports more than one server. In
    such a configuration, you can specify the server to which the
    application is directed. If you do not specify the display-
    device parameter, the SET DISPLAY/SERVER command associates the
    server with the display device indicated by the logical name
    DECW$DISPLAY.