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

    Tells the class driver to initiate the path selection process
    immediately. If this qualifier is omitted when a new host name
    is specified, a switch from the current path to the new preferred
    path will not occur until some other event initiates the path
    selection process.