From: craig@osh3.OSHA.GOV (Craig Nordin)
Subject: Re: NCR 3450 powerfail options
Organization: U.S. D.O.L - Occupational Safety & Health Admin.
Date: Thu, 07 Jan 1993 01:44:26 GMT

Hi, 

I might have written to you before, but I might not have.
We've installed 50 of 250 3445 systems around the country so
far.  I'm always interested to hear about their "cousins".

You wrote: 

>The 3450 powerfail kit offers restoration of the system to exactly
>where it was before the power failed.

I saw this in action and it looks nice.  But I forget how long it
will go on without power.  If I remember right, it goes for about
30 seconds.  

I can only guess about how you are putting these things into action.
It seems to me that you really have to take a "whole system" approach
to your decision.  

For instance, if your NCRs directly support the cash registers is
the WHOLE THING line conditioned and UPS'ed already?  I mean if your
NCR goes down quick (like I think it would with Powerfail alone) and 
freezes a transaction half-entered by the clerk while the cash register 
itself has ten minutes of power, you might need something else 
(add a UPS to the NCR and maybe forget the powerfail).

The other thing I can figure needs some analysis is the applications
you have on the NCR.  I don't know what functional business systems
you have on the NCR, but I'll guess some of them are more or less
"real-time", meaning your company gets burned if the kernel seizes.
When I write my applications and programs, I keep in mind how they
might get shut-down mid-stride -- so nothing terrible happens when
they get the old SIGHUP. If the particular program is working with
touchy data, it will have a cleanup routine that handles the 
various "soft" shutdown signals.  And even if they get kill -9, 
they can, oh, maybe figure out where they left off when they come
up, and execute each whole transaction in one, tight little 
split-second (meaning a very very very rare chance of catching
the program's execution mid-stride).

Seems to me that powerfail and UPS is the safest.  But you have
to reboot the machine once in a while anyhow.

Our production sites (where the NCRs have to do their business)
are in small or mid-sized offices where a power failure is a
rare thing (except for two small sites).  We have a UPS hooked
up that will notify the system to do an orderly shutdown when
the power goes off.  

There is even a UPS monitor software package available in 
comp.sources (although our integrator didn't use it).  From
looking at the NCR manuals and the comp.sources software the
UPS monitor stuff is fairly easy.  It checks every once in
awhile for a power change (through the serial port in the
back of the NCR box) and then times the "out time".  The 
monitor s/w has a certain "grace" period, in which the
main power has a chance to come back on, then it gives
warning to all users, and then signals the kernel to do 
an orderly shutdown.  

I think there is even a specific signal() value in the 
C library to identify power failure, so any C (or other
language) program could check the power status if it 
needed to. [ SIGPWR? ]

The powerfail option was not worth it for us, when we 
considered it.  I'd guess that the business work being
done with the NCR (as well as the rest of the "whole" system)
will pretty much decide for you what the best decision
is.

We had to have the UPS because we wanted to warn the users
that the system was going down -- so that they could save
their work if neccessary.  Besides, in the small offices,
that UPS buzzer is nasty-loud enough anyhow.

>Being long term Tower users we would prefer the system to be restored
>to its original state but have heard that the 3450 powerfail kit is
>much more expensive than a separate UPS.  Any comments on this?

Maybe the powerfail kit INCLUDES a UPS.  I don't know.  I'm sure
the powerfail is MUCH more expensive.  I think they put in a
rather hefty and complex card in the NCR box to make it all
work.

>Also, on initial work with the 3450 it seems that the 3450 powerfail
>set up is a closely tied component of the 3450, are there any problems
>with not using it?

Other than the loss of that "restored to EXACTLY the same state" part,
I don't think so.

The standard manuals that come with the NCR's show the pinouts for
the serial/power failure alarm connection, so all you should need
is any UPS that will hook up to a serial port and some sort of
UPS monitor software.  Don't get me wrong, it is some work, but
you might save some money and be more certain about the whole
shutdown process if you put it together yourself.

Ours is an SPS/American Power Conversion, Backup/RT 8000, you might
price it to compare it to what NCR might offer.   Ours is supposed
to go solid for at least 10 minutes (if not 30).  That is long
enough for the shut-down process to take place.

Another thought:  We don't plug all of our terminals into the
UPS (that would be overload!), so that means their sessions
are inaccessible after initial power failure anyway.

This power failure business is tricky and unforgiving. Good Luck.

Please let me know how you do it.

Have a good day....


P.S.  Don't forget to add the cost of a good UPS battery maintenance
plan to the whole dang thing, or else, two years from now your grand
scheme of reliability will all be for waste...

 -
 US Department of Labor      Craig Nordin          craig@osh3.osha.gov
 OSHA OMDS FSDB #N3661                  uunet!osh1.osha.gov!osh3!craig 
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