PWRDWNSYS RESTART(*YES) didn't restart]

Greetings,

The other morning, a customer machine as part of a regularly
scheduled BRMS job powered down with RESTART(*YES). The restart
did not happen. The customer would like an explanation, and I do
not have one to offer.

From the help information of the PWRDWNSYS command, I understand

that a lack of utility power would be a legitimate explanation
for the system staying down. Looking into the log for msgids
CPF1816 and CPF1817, I see typically that utility power goes off
for under a minute a couple of times a week.

So, I ask those who might know, for how long during the "bounce"
could a failure of utility power happen without logging a
CPF1816?

Is there anything else I can look for?

The machine in question is a model 820 running V5R2.

Thank you, all, for your attention.
Terry.