From: jeh@cmkrnl.com
Newsgroups: comp.os.vms
Subject: Re: How Open is Open VMS?
Date: 1 Jan 93 00:45:08 GMT
Organization: Kernel Mode Consulting, San Diego, CA

In article <1992Dec31.190236.29454@zooid.guild.org>, Mark Kovarski <kovarski@zooid.guild.org> writes:
> 
> Could someone tell me how "open" Open VMS really is. Is it so open that
> someone can obtain the source codes, or is it another proprietary operating
> system with the word "Open" attached to it? Thanks.
> 
> Mark K.
> E-Mail: kovarski@zooid.guild.org

VMS is just as proprietary as, for example, SCO Unix, SunOS, HP-UX, etc.  

Nonetheless, listings of VMS (not just the executive, but nearly everything
that ships with the system) are available on CD-ROM for a little over $2K. If
you are interested in this level of information about VMS, there are several
excellent books from Digital Press: _VMS Internals and Data Structures_ by Ruth
Goldenberg et al., and _VMS File System Internals_ by Kirby McCoy.  If these
prove to be tough to navigate without a guide, DEC offers several courses on 
VMS internals.  

Digital is clearly committed to continuing to provide this level of "internals"
documentation:  Two preliminary sections of the ~"VMS for Alpha Platforms
Internals" book have been published, and a book on VMScluster internals is
coming out this Spring (preliminary version was available at the Fall 92 DECUS
Symposium). 

Last I heard, source kits (from which you could build a modified exec) were
$25K.  This product has not been kept up to date; it's a major pain in the neck
to produce (it is not just a snapshot of the VMS master source volume) and 
there aren't enough buyers for DEC to continue doing this.  

It is generally not necessary, though, to recompile nor even to relink any part
of VMS in order to add to it or change it.  In particular, device drivers can
be added to a live running system.  You can even replace an old version of a
driver with a newer one on a live system.  

So.  Is VMS "open"?  If "open" means lots of well-documented hooks for adding
things like device drivers, system service calls, a replacement scheduler,
etc., with easy access to listings to see how VMS does things, then the answer
is yes -- in fact, on this score, VMS has long been far more "open" than any of
the proprietary versions of Unix (not to be confused with the recently-released
public-domain version of BSD Unix) ever thought of being. 

If "open" means "possibility of porting to a non-Digital hardware platforms",
yes, it's technically possible, and DEC is interested in pursuing this with
hardware vendors. 

If "open" means "is available right now for non-Digital hardware platforms",
then no, VMS isn't "open".  Which means, if you build applications that take
advantage of VMS features for which there are no parallels on O/S's for other
machines, you're not going to be able to port those applications to those other
machines very easily. 

If "open" means "adherence to standards", the answer is of course "which 
standards"?  The Software Product Description for VMS has a LONG list of
standards with which VMS complies.  There are others to which it does not
comply.  For example, VAX C, which until very recently was the only C compiler
available from Digital for VAX/VMS, is not Ansi-C-compliant.  

	--- Jamie Hanrahan, Kernel Mode Consulting, San Diego CA
drivers, internals, networks, applications, and training for VMS and Windows-NT
uucp 'g' protocol guru and release coordinator, VMSnet (DECUS uucp) W.G., and 
Chair, Programming and Internals Working Group, U.S. DECUS VMS Systems SIG 
Internet:  jeh@cmkrnl.com, hanrahan@eisner.decus.org, or jeh@crash.cts.com
Uucp:  ...{crash,eisner,uunet}!cmkrnl!jeh

"Openness is in the eye of the beholder.  Or maybe in the wallet."