System Startup, Configuration, and Shutdown Reference Manual (32650-90892)

Appendix G 233
UPS and UPS Monitor/iX Software
Configuring a UPS Device
continues to operate. However, the actual behavior of the system will vary depending on
how much of the system equipment is provided with UPS power.
In the “minimal” case, where only the SPU and any Remote Busses receive UPS power
(and assuming that disks are external to the SPU), the system is most likely to appear to
be dormant (like a traditional battery backup method system) because the system can not
make progress once the disks lose power and spin down. The system will simply enter its
“idle loop”, waiting for disk I/O operations to complete, and that won't happen until AC
power returns and the disks spin up again.
But in expanded UPS coverage systems, where some or all of the disks receive UPS power,
the system may continue to run to some extent. Again, it depends on what resources the
system needs to perform its workload. Batch jobs that only need CPU, memory, and disk
I/O can continue to run undisturbed. Processing that requires tape or printer or terminal
I/O will be blocked if those peripherals do not have UPS power.
UPS Monitor/iX issues a warning message to the system console to notify the operator that
the particular UPS (identified by its LDEV number) has reported to the system that its
input AC power has failed. In Example G-1, UPS Monitor/iX reports and power failure and
a recovery shortly thereafter:
Example G-1. Sample Console Messages from UPS Monitor/iX
:showtime
FRI, AUG 13, 1993, 11:27 AM
:
:11:27/50/UPS LDEV 102 reports loss of AC input power. (UPSERR 0033)
**RECOVERY FROM POWER FAIL**
11:27/50/UPS LDEV 102 reports AC input power restored. (UPSWRN 0036)
:
UPS Monitor/iX also writes a system log file entry that denotes the input power loss to the
UPS device. Read “To enable logging of UPS activity” and “To review UPS activity recorded
in the system log file,” later in this chapter for more information.
System Behavior When AC Power Returns
The behavior of the system when AC input power returns to the UPS is very similar to
that of the battery backup method systems. One of two things will happen: a recovery from
power failure (if AC power returns before the UPS battery that backs up the SPU becomes
exhausted) or a system crash.
If AC power returns before the UPS battery becomes exhausted (up to fifteen minutes
when starting with fully charged UPS batteries; less if the batteries were already partially
discharged), then the system recovers from the AC power failure and resumes normal
operation. In this case, UPS Monitor/iX displays a message on the system console, posts an
entry in the system log files, and broadcasts the following message to all active user
terminals:
** RECOVERY FROM POWERFAIL **