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- Path: sparky!uunet!spool.mu.edu!agate!ucbvax!galaxy.dnet!gleeve
- From: gleeve@galaxy.dnet
- Newsgroups: comp.os.vms
- Subject: Re: movefile query
- Message-ID: <9301041506.AA12651@relay1.UU.NET>
- Date: 4 Jan 93 14:26:21 GMT
- Sender: daemon@ucbvax.BERKELEY.EDU
- Distribution: world
- Organization: The Internet
- Lines: 31
-
- There are a couple longs for additional operation status codes in
- a FIB. The Movefile primitive uses one of these (see the i/o support
- manual chapter on ACP interface for detail) to report what the
- movefile actually did.
-
- Incidentally, I have implemented a softlink facility for VMS, embedded
- in the filesystem, using some of the techniques described in the last
- magic session at DECUS. (<evil grin for those who wanted humor and
- didn't listen...you'll have to wait for the next symp. where I can
- give a regular session...>). Unfortunately, not being DEC, it doesn't
- er, I didn't use the normal directory file hooks...can't easily break
- into the relevant parts of RMS. (Pardon the garble...someday I'll compose
- using an editor :-) ).
- Forcing an open of another file is simple. The tricky stuff is handing
- the markings in some kind of sensible way and getting the user channel
- back where he expects it when close occurs. Fail to do that and all sorts
- of odd, but generally harmless, things happen.
- There are conceptual issues too. On a VMS system, you can reasonably want
- a link not to a device, but to a volume on that device. It's interesting to
- check for these, but has to be a user option; imagine the pathological
- case in which your hard disk farm has a bunch of softlinks to files on
- different floppies, and only one floppy drive. Lots of deadlock possibilities
- exist where applications try to open different combinations of files on
- different volumes; fielding things correctly would require intercepting
- read/write virtual and ensuring the correct volume was there before allowing
- things to proceed. While this can be done, it's questionable whether anyone
- would actually want to do it. ("seek time" takes on a whole new meaning when
- it means rummaging thru a pile of floppies :-) for such a case...)
- Glenn
- Everhart@raxco.com
-
-