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

    Default: None          Value: Local entity name

    Local entity name of the the Physical layer entity over which the
    HDLC protocol is to operate.

    This characteristic must have a value before the HDLC link is
    enabled. You can modify this characteristic only when the entity
    is disabled.