[Info-vax] Reimplementing VMS, was: Re: HP adds OpenVMS Mature Product Support beyond the end of Standard Support

[Simon Clubley]

On 2014-02-04, Bill Gunshannon <bill at server3.cs.scranton.edu> wrote:
>
> So, based on more recent comments here, I draw these conclussions.
>
> 1. Actually porting the original VMS, while probably possible, is not
> a practical solution.
>

Totally agree with this; this is simply not a viable option.

> 2. Apparently the idea that nothing but the original VMS is capable of
> doing the job is no longer true.
>

I have not thought that was true for many years now.

> 3. A VMS API and userland running on some other underlying kernel would
> meet the needs and satisfy the majority of remaining VMS users.
>

I don't know here if you still think of a microkernel as just another
Unix style kernel. If you still think this, you _really_ need to do
some reading/research on microkernels because you are _way_ wrong.

A POSIX level VMS API emulation is absolutely not, in any way, shape or
form, even the slightest bit comparable to the servers/tasks you would
implement on top of a microkernel to produce something which looked
like VMS to the userland applications.

> 4. "a re-implementation of vms system services, rtl, etc, has been done,
> using unix ipc mechanisms, etc
>

That's a viable option if all you do want is a POSIX level emulation
on top of a Unix kernel and is another option to be considered.

However, that is not what people like myself are talking about when
suggesting a microkernel approach.

> Which leads us to the question:  Why is there not already a group
> working on an Open Source Complete VMS API capable of running on
> top of any POSIX infrastructure?  This would allow to pick their
> underlying architecture based on their needs, be it: Linux, BSD,
> Solaris, Mach, whatever.  Seesm this would make more sense than
> the current "porting project" that meets several times a month.
> And could be accomplished by pretty much the same people.
>

Once again, talking about running a VMS layer on top of a POSIX base
makes sense when your underlying operating system is Unix but it
makes no sense when talking about reimplementing VMS on top of a
microkernel. In the latter case, the operating system _is_ (New)VMS,
not Unix; it's just that it's implemented on top of a microkernel
instead of the underlying physical hardware.

If you don't understand this, then you have your abstraction layers
all confused.

Simon.

PS: And as for real time latency issues, once again don't forget QNX
is implemented as a microkernel architecture. That's no guarantee it's
possible with the FreeVMS design, but the QNX case does show that
it's something which is not impossible to achieve.

-- 
Simon Clubley, clubley at remove_me.eisner.decus.org-Earth.UFP
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