Lock logical record set (INT 21h, D1h - Novell NetWare 4.6)

        Entry:
          AH = D1h
            if function C6h lock mode 00h:
               DL = mode
                     00h  No wait
                     01h  Wait
            if function C6h lock mode 01h:
               BP = timeout in timer ticks (1/18 sec)
        Return:
          AL = error code