Library /sys$common/syshlp/dbg$help.hlb DEBUG, Messages, NOSUCHWIND  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 no such window defined: display_name

    Facility: DEBUG, VMS Debugger

    Explanation: The specified, or defaulted window <window_name,
    !AC> does not exist.

    User Action: Reenter the command, specifying an existing window
    name.