We had a situation 2.5 weeks ago with a power outage that went like this:

1) System was in restricted state doing backup, ie, no power handling
program active
2) 3:45am power went out
3) 4:05am the system powered off because UPSDLYTIM was set to 1200 (Next
day, the BRMS log showed that the last item in the control group had been
4) Utility power "restored" at 1pm, but we didn't bring anything up because
of power instability. It made the UPS really cranky.
5) Utility power finally restored properly at 7pm
6) We brought up the Windows servers at that time
7) Because it was late, we didn't bring up the System i 520 until 7am the
next morning so we would be fresh. First in manual mode, then normal mode.
Everything was OK and no issues since.

This was about 27 hours from power outage until we actually brought the
system up again. I'm guessing the UPS batteries probably went dead before
1pm (when unstable utility power came back).

Would the cache batteries have held properly from whenever the UPS
batteries went dead until 1pm?

When unstable utility power was restored at 1pm (9 hours), then some power
would have been coming from the UPS. Since nothing else on the UPS was
powered on, I assume whatever little power was available from the UPS would
have been enough to power the control panel/service processor/green light
on the front of the system and therefore would be supplying power to the
cache batteries.

Does what I just wrote make sense?

On Wed, Jan 16, 2013 at 1:23 PM, Sue Baker <smbaker@xxxxxxxxxx> wrote:

On 1/16/2013 3:37 AM, Paul Fenstermacher wrote:
Ending the system "controlled" flushes the disk cache from memory to
> "immediate" does not do this.

Nope, not a fact.

The disk IOAs need time to write the contents to disk. Ending
controlled allows for the IOA to do its normal thing and put data onto
disk just as it would if the system were running.

For most IPLs, it really doesn't make any difference because you're
likely bringing the system right back up. It is when you are shutting
down and not planning to bring the system back up for days or weeks when
it will be important to make sure the contents of cache get written out.
Maybe Ias a precautionary measure due to an impending natural disaster
like a hurricane?

Another time when you want to make sure the cache is written is if you
will be relocating the IOAs and disk behind them to another system. My
advice to make sure it happens is to end controlled, IPL to DST,
shutdown, IPL to DST again, and finally shut down. I don't remember the
specifics now, but the multiple IPLs to DST do something to make sure
every bit gets written to disk.

Sue Baker
IBM Americas ATS - Power Systems
Rochester, MN
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