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

       /JSB
       /NOJSB

    (VAX only) Qualifies a previous SET STEP INTO command or a
    current STEP/INTO command.

    If execution is currently suspended at a routine call and the
    routine is called by a JSB instruction, STEP/INTO/NOJSB has the
    same effect as STEP/OVER. Otherwise, STEP/INTO/NOJSB has the same
    effect as STEP/INTO.

    Use STEP/INTO/JSB to override a previous SET STEP NOJSB command.
    STEP/INTO/JSB enables STEP/INTO to step into routines called
    by a JSB instruction, as well as into routines called by a CALL
    instruction.

    The /JSB qualifier is the default for all languages except
    DIBOL. The /NOJSB qualifier is the default for DIBOL. In DIBOL,
    application-declared routines are called by the CALL instruction
    and DIBOL Run-Time Library routines are called by the JSB
    instruction.