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

  all> 2,3> GO;WAIT
  processes 2,3
    break at CLIENT\main\%LINE 18814
        18814:      status = sys$qiow (EFN$C_ENF,  mbxchan,
                          IO$_READVBLKIO$M_WRITERCHECK, myiosb)
  process 1
    break at SERVER\main\%LINE 18834
        18834:             if ((myiosb.iosb$w_status ==
                          SS$_NOREADER) && (pos_status != -1))
  all>

      This command sequence executes the target processes (in this
      case, 2 and 3), and the debugger waits until both processes
      reach breakpoints before prompting for the next command.