VMS vs. UNIX file system

[Carl M. Fongheiser]

In article <69166 at sun.uucp> guy at gorodish.Sun.COM (Guy Harris) writes:
>> But...the user can't necessarily replace RMS without getting to write
>> his own CHME dispatch table, something the kernel is not likely to let
>> him do.
>
>This depends on what you mean by "replace".
>
>Under RSX-11, you can presumably "replace" RMS, in the sense of having a
>package that does the same general sort of function, without being able to get
>at a more privileged mode.  If an RMS-like package doesn't require QIOs that
>can be run only from executive mode, you could do the same under VMS (although
>I wouldn't put it past DEC to have stuck in executive-mode-only QIOs which RMS
>uses).

As a matter of fact, RMS does *not* do anything you can't do in user mode.
All of the QIO's for reading and writing file attributes are available in
user mode.  The only thing that makes having RMS run in executive mode
worthwhile is that open files can persist past the activation of a single
image.  (Remember that VMS processes typically last a lot longer than Unix
ones, normally from login to logout).  The tricky part about replacing RMS
is doing record-locking, since that's a concept foreign to the ACP itself.
Also note that in Version 4.0 and later, many of the system services use
RMS themselves.

				Carl Fongheiser
				University of Pittsburgh
				...!pitt!cisunx!cmf
				cmf at unix.cis.pittsburgh.edu
				cmf at PITTUNIX.BITNET