[Info-vax] Kittson question

[johnwallace4 at yahoo.co.uk]

On Sunday, 4 January 2015 15:22:30 UTC, Jan-Erik Soderholm  wrote:
> Scott Dorsey skrev den 2015-01-04 15:33:
> > JF Mezei  <jfmezei.spamnot at vaxination.ca> wrote:
> >> In cases where the customer wants you to perfectly and completely mimic
> >> their current VAX down to device names etc, is this not an indication
> >> that the customer no longer has in-house VMS maintenance expertise and
> >> prefers to pay you more to mimic the environment so no changes need to
> >> be made ?
> >
> > Yes, or even worse he has software that he doesn't understand and cannot
> > change.  Often this is commercial software for which source was never
> > available, or locally-written code for which the source has been lost.
> >
> >> In a situation where someone setting up a new VMS box on that new
> >> architecture I can't name,  wouldn't that imply an active VMS site with
> >> in-house expertise who would be able to move their last VAX apps onto
> >> any emulated instance and change device/disk names if needed ?
> >
> > Not necessarily.  Could be an outside consultant coming in and doing the
> > job and working to get out as quickly as possible.
> >
> >> In other words, when looking at providing emulated VAX-VMS support on
> >> the new VMS, is it really necessary to be able to mimic every different
> >> VAX model with every different config ? Wouldn't a generic VAX emulation
> >> based on one of the last VAX models be more than enough since anyone
> >> setting it up will have the knowledge to tailor their VAX-VMS apps ?
> >
> > I don't think so, but it might be nice and it might make life easier for
> > some customers.  I think this is much more an issue for ELN and Ultrix
> > users than VMS, but I don't think there are any of those left.
> 
> I know a fairly large site which uses VAXeln for the factory
> control systems manufacturing kitchen equipment.
> 
> 
> > --scott
> >

Exactly. VAXeln has the capability to be fit and forget, as much as
or maybe even more than VMS does/did. Any VAXeln systems that are still
around stand an excellent chance of being almost invisible. 

Unless a VAXeln application deliberately contains unusually
hardware-specific code, the only real hardware dependence in a VAXeln
system are the OS kernel's hardware-dependent pieces (the ones which
in a VMS system might iirc live in SYSLOAxxx?). In a VAXeln system,
the developer picks the relevant hardware=specific bits when the system
image is configured. Unlike VMS, there's no boot-time mechanism for
choosing the relevant hardware-specific bits for the OS. 

If the hardware is emulated rather than real, the VAXeln system just
needs the emulator to look sufficiently like the originally chosen
target. On the surface it doesn't sound as though it needs any
particular magick.

Of course if it's a genuine real-time VAXELN system running in an
emulator on top of Windows, and Windows decides to take a break from
running the emulator for a few hundred milliseconds (as it does),
*that* might sometimes be exciting. Or sometimes it might have no
visible effect.

Have a lot of fun.