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

       /SYSTEM (default)
       /NOSYSTEM

    Qualifies /INTO. Use with /INTO and one of the following
    qualifiers:

       /BRANCH
       /CALL
       /INSTRUCTION
       /INSTRUCTION=(opcode[, . . . ]) (VAX only)
       /LINE
       /VECTOR_INSTRUCTION (VAX only)

    The /SYSTEM qualifier permits the debugger to break within system
    routines (P1 space) as well as other routines. The /NOSYSTEM
    qualifier specifies that breakpoints not be set within system
    routines.