/sys$common/syshlp/helplib.hlb SET, TERMINAL, Qualifiers, /SWITCH  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /SWITCH=DECNET

    On VAX, causes the terminal lines at each node to be switched
    to dynamic asynchronous DDCMP lines, when specified with
    the /PROTOCOL=DDCMP qualifier. Note that /SWITCH=DECNET is a
    permanent characteristic; therefore, the /PERMANENT qualifier is
    not required.