[Info-vax] Kittson question

[Bob Gezelter]

On Sunday, January 4, 2015 6:10:59 AM UTC-5, JF Mezei wrote:
> On 15-01-02 12:46, Stanley F. Quayle wrote:
> 
> > No, it doesn't. Check out www.stanq.com/wf1.html  They saved floor space, power, and air conditioning. They improved performance greatly.
> 
> 
> 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 ?
> 
> 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 ?
> 
> 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 ?
> 
> Being able to set model name for license purposes is different, I am
> talking about the actual emulation software and the hardware it
> virtually creates.

JF,

No it is not necessarily a lack of expertise and experience. It is a cost tradeoff.

In some client situations, I have had to use the ASSIGN/SYSTEM/MODE=EXEC/... option (in one memorable case, we were resurrecting an old system, and the secondary disk controller failed; so I created alternative logical disks on the first controller and used the ASSIGN trick to avoid a detailed analysis of fixing all of the references). Such situations occur more often than one would like.

In many environments, configuration management rules prevent changes in device names. Prevent may be a bit strong, but the economics are severe. An emulator with the same virtual configuration as the original environment would likely be exempt from a re-certification requirement. In a large system, re-certification is a MAJOR project.

It is also a question of time. An emulator faking device names can be installed quickly. Examination and changes of source code is a far more involved exercise. As before, this decision is a technical/economic decision, not a strict technical call.

It is also not new. I used RSX-11 redirects to do much the same thing back in the 1980's. RSX-11 did not have logical names (at that time), programs often had hardcoded device references. Upgrading /changing hardware would change device names, causing problems. References to permanently redirected names resolved (pardon the pun) that problem.

- Bob Gezelter, http://www.rlgsc.com