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

       /PENDING=identification-number

    Requires OPER privilege.

    Sends a message to the user specified by the identification
    number and prevents the user from entering other commands until
    the operator fulfills or aborts the request. The current terminal
    must be enabled as an operator terminal.