NetNews Usenet Archive 1992 #18/NN_1992_18.iso/spool/comp/sys/dec/4498

Text File | 1992-08-12 | 1.8 KB | 43 lines

Newsgroups: comp.sys.dec
Path: sparky!uunet!decwrl!deccrl!news.crl.dec.com!rdg.dec.com!ryn.mro4.dec.com!news
From: [e-mail] (Blair Phillips - Digital)
Subject: Re: How to read/write VMS (RMS?) disk blocks asynchronously
Message-ID: <[e-mail]>
Lines: 30
Sender: [e-mail] (USENET News System)
Reply-To: [e-mail]
Organization: Digital Equipment Corporation
References:  <[e-mail]>
Date: Thu, 13 Aug 1992 00:23:35 GMT


In article <[e-mail]>, [e-mail] (Mark R. Ludwig) writes:
>
>I'm looking for RTFM pointers.
>
>I currently have a Fortran application using $READ and $WRITE
>(SYS$READ and SYS$WRITE, actually) to read and write file blocks.  The
>higher-level application supports the idea that I/O may be
>asynchronous for better throughput by overlapping computing with I/O.
>
>I've read much of the RMS Reference, and concluded that the
>asynchronous support there is quite limited, because it only allows
>one operation at a time (on a FAB, or RAB, I forget exactly which).
>For our application it is not feasible to have multiple FABs or RABs
>for a single file.
>
The simplest way to do what you want is to open the file using RMS specifying
the User File Open option (UFO) in the FOP field of the FAB. The channel number
assigned is returned in the FAB$L_STV field, and you then use that to do
normal $QIO's on the file. As long as you stick to virtual i/o (i.e. block
specified within the file) no special privs. are needed.

There are a few caveats - look up the RMS manual for details.

--
----------
Blair Phillips                    [e-mail]
Digital Equipment Corp (Aust) P/L        Phone: [phone]
7-11 Barry Drive, Turner, ACT 2601 AUSTRALIA    FAX  : [phone]