Xref: utzoo comp.unix.wizards:11132 comp.os.vms:8665
Path: utzoo!attcan!uunet!husc6!ukma!tut.cis.ohio-state.edu!bloom-beacon!bu-cs!bucsb!jbw
From: jbw@bucsb.UUCP (Joe Wells)
Newsgroups: comp.unix.wizards,comp.os.vms
Subject: Re: VMS vs. UNIX file system
Summary: ASTs, directory links, stack unwinding
Message-ID: <1986@bucsb.UUCP>
Date: 14 Sep 88 21:42:52 GMT
References: <411@marob.MASA.COM> <178@arnold.UUCP>
Reply-To: jbw@bucsf.bu.edu (Joe Wells)
Followup-To: comp.unix.wizards
Organization: Boston Univ Comp. Sci.
Lines: 49

In article <178@arnold.UUCP> dave@arnold.UUCP (Dave Arnold) writes:
>VMS's strengths?
>AST's, Timer queues, condition handling, exit handling, message
 ^^^^^                ^^^^^^^^^^^^^^^^^^
>facility.

ASTs are for me VMS's greatest advantage.  The ability to have
multiple system calls outstanding at one time is a godsend for
realtime control systems.  Running a separate process for each
blocking task and using IPC just doesn't cut it.

Stack unwinding is really nice too.  The ability in LISP to abort
instruction sequences with "throw" and have everything clean itself up
as the stack is unwound is *very* powerful.  In addition, you can post
your own unwinding cleanup instructions.  Under VMS, you can do this
in *any* language.  The operating system and the VMS procedure
calling standard provide for generic stack unwinding.

Directory links under VMS are not necessary for a file to exist.
Under UNIX, when all the links to a file disappear, and all processes
close the file, the file is deleted.  In VMS, a file can exist without
a name.  It can be accessed by its unique file identifier.  In
addition, the problem of dangling directory links to deleted files
does not exist.  When the VMS equivalent of the UNIX inode is reused,
a counter in the index table slot is incremented.  Thus any dangling
pointers to the previous file that used the same slot won't have any
effect.

I would be much happier with the UNIX environment if it supported
these features, but then if money grew on trees, I probably couldn't
climb them.  I'm also not trying to imply that VMS doesn't have more
than its own share of ridiculously stupid features.

>Other VMS pitfalls?
>The resource quota system!!!!!!!
>How often have you written a program, and got the famous:
>%SYSTEM-F-EXCEEDED QUOTA
>message?  Isn't it fun trying to figure out which bloody quota
>was exceeded?!  Stupid!

Good lord!  Don't remind me of this!  What a royal pain in the *ss!

>-- 
>Dave Arnold
>dave@arnold.UUCP	{cci632|uunet}!ccicpg!arnold!dave

Joe Wells
UUCP: ...!harvard!bu-cs!bucsf!jbw
INTERNET: jbw@bucsf.bu.edu