Library /sys$common/syshlp/nclhelp.hlb show, x25_access, dte_class, Status  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 o  usable dtes

    Set of DTEs that are enabled and belong to this DTE class. For
    outgoing calls, a DTE is picked from this set if it is eligible
    (that is, if its status attribute state is set to running). If
    there is more than one eligible DTE, a round-robin algorithm
    is used to select one of the eligible DTEs. A DTE is added to
    the set when it is enabled, and is removed from the set when
    it is disabled (see the enable x25 protocol dte and disable x25
    protocol dte commands).