Library /sys$common/syshlp/nclhelp.hlb set, routing, circuit, reserved_adjacency  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Support: End
    Default: False         Value: True or false

    If true, specifies that one SVC must be reserved for connection
    to a router. If false, no SVC needs to be reserved for
    this purpose. This characteristic is supported only if the
    circuit's characteristic type is x25 da). You can modify this
    characteristic only when the entity is disabled.