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

       /SYSTEM (default)
       /NOSYSTEM

    Qualifies a previous SET STEP INTO command or a current STEP/INTO
    command.

    If execution is currently suspended at a call to a system
    routine (in P1 space), STEP/INTO/NOSYSTEM has the same effect
    as STEP/OVER. Otherwise, STEP/INTO/NOSYSTEM has the same effect
    as STEP/INTO.

    Use STEP/INTO/SYSTEM to override a previous SET STEP NOSYSTEM
    command. STEP/INTO/SYSTEM enables STEP/INTO to step into system
    routines, as well as into other kinds of routines.