register save mask hidden for stack frame frame_number

    Facility: DEBUG, VMS Debugger

    Explanation: Information on where the designated routine
    invocation might save registers is in a module which has not
    been set. Symbolic references to non-static variables of callers
    of this routine may not be resolved correction by the debugger.

    User Action: Set the module by using the SET MODULE or SET
    MODULE/CALLS commands, or enable dynamic module setting with the
    SET MODE DYNAMIC command. Then retry the action which produced
    this message.