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

    Requires OPER (operator) privilege.

    Broadcasts a message to all terminals that are attached to the
    system or cluster. These terminals must be turned on and have
    broadcast-message reception enabled. The /ALL qualifier is
    incompatible with the /USERNAME and /TERMINAL qualifiers.