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

    alias

       Specifies the name of the remote VT application that you wish
       to connect to.  This name can be an alias in the
       SYS$COMMON:[SYSEXE]ISOAPPLICATIONS.DAT file, or it can be the
       X.500 Distinguished Name of the remote VT application enclosed
       in quotes.