NonStop Operations Guide for H-Series and J-Series RVUs

controllers before the ServerNet was shut down in order to achieve a relatively clean shutdown.
This makes TMF recovery less time-consuming and difficult than if all power failed, the NonStop
OS crashed, and disk writes did not complete.
NOTE: OSM power fail support works as described only after it has been properly configured,
as described in “Configure OSM Power Fail Support” (page 173).
When OSM determines that all P-switches or ServerNet switches are running on UPS power, OSM
recognizes this as a power outage and logs an event indicating the beginning of the ride-through
time period, which was specified during configuration. OSM monitors whether AC power returns
before the ride-through period ends, and acts accordingly:
• If AC power is restored before the ride-through period ends, the ride-through countdown is
terminated, and OSM does not take further steps to prepare for an outage.
• If AC power is not restored before the ride-through period ends, OSM broadcasts a
PFAIL_SHOUT message to processors (the processor running OSM is the last one in the queue)
to shut down the system's ServerNet routers and processors in a fashion designed to allow
completion of disk writes for items in transit through controllers and disks.
NOTE: Do not turn off the UPS as soon as the NonStop OS is down. The UPS continues to supply
power until that supply is exhausted, and that time must be long enough for disk controllers and
disks to complete disk writes.
NonStop Cabinets (Modular Cabinets)
NonStop NonStop systems are designed to operate in a computer-room environment containing
a site UPS. Without a UPS, a system will stop uncontrollably when the power is lost. An optional
UPS module can be installed in a modular cabinet to provide power if no site UPS is available.
If AC power to a NonStop system is lost, the system will shut down after a preset time as long as
UPS power is available. If the system shuts down, it will be necessary to restart the system manually
when AC power is restored.
If modular cabinets lose power without a UPS, recovery of lost data will be difficult and files might
be corrupted.
Regardless of system power-fail scenario, if site air conditioning fails and the computer-room
temperature rises, the system might shut itself down uncontrollably as each processor reaches its
critical temperature. Refer to the Planning Guide for your NonStop system.
NonStop S-Series I/O Enclosures
NonStop S-series I/O enclosures have internal batteries and do not require a UPS. NonStop S-series
enclosures must shut down before their battery power is lost. For information about power fail for
I/O enclosures, refer to the NonStop NS16000 Series Planning Guide.
External Devices
External (peripheral), devices, such as tape drives, external disk drives, LAN routers, and SWAN
concentrators, are not backed up by internal batteries. External devices behave differently than a
system during power failure according to the UPS support provided:
Peripheral devices will fail immediately if not supported by
a UPS.
No UPS
A site UPS should support external devices until its capacity
to supply power is exhausted.
With a Site UPS
An optional internal UPS will not support external devices
during power failure.
With an Internal UPS
System Response to Power Failures 171