On Alpha and Integrity server systems, starts a Fast I/O
    operation. The $IO_PERFORMW service completes synchronously;
    that is, it returns to the caller after performing the Fast I/O
    operation.

    In all other respects, $IO_PERFORMW is identical to $IO_PERFORM.
    For all other information about the IO_PERFORMW service, see the
    help for $IO_PERFORM.

    Format

      SYS$IO_PERFORMW  fandle ,chan ,iosadr ,bufadr ,buflen ,devdata

    C Prototype

      int sys$io_performw  (unsigned __int64 fandl, unsigned short

                           int chan, struct _iosa *iosadr, void

                           *bufadr, unsigned __int64 buflen, unsigned

                           __int64 devdata);