Sun Microsystems Enterprise 250 Owner's Manual page 62

Memory modules
PCI buses
System I/O interfaces
The automatic system recovery feature allows the system to resume operation after
experiencing certain hardware faults or failures. Automatic self-test features enable
the system to detect failed hardware components and an auto-configuring capability
designed into the system's boot firmware allows the system to deconfigure failed
components and restore system operation. As long as the system is capable of
operating without the failed component, the ASR features will enable the system to
reboot automatically, without operator intervention.
During the power-on sequence, if a faulty component is detected, the component is
effectively disabled and, if the system remains capable of functioning, the boot
sequence continues. In a running system, some types of failures (such as a processor
failure) will usually bring the system down. If this happens, the ASR functionality
enables the system to reboot immediately if it is possible for the system to function
without the failed component. This prevents a faulty hardware component from
keeping the entire system down or causing the system to crash again.
Control over the system's ASR functionality is provided by a number of OpenBoot
PROM commands. These are described in the document Platform Notes: Sun
Enterprise 250 Server, available on the Solaris on Sun Hardware AnswerBook. This
AnswerBook documentation is provided on the SMCC Supplement CD for the
Solaris release you are running.
Hardware Watchdog Mechanism
To detect and respond to system hang conditions, the Enterprise 250 server features
a hardware watchdog mechanism—a hardware timer that is continually reset as long
as the operating system is running. In the event of a system hang, the operating
system is no longer able to reset the timer. The timer will then expire and cause an
automatic system reset, eliminating the need for operator intervention.
Note – The hardware watchdog mechanism is not activated until you enable it.
To enable this feature, you must edit the /etc/system file to include the
following entry:
set watchdog_enable = 1
This change does not take effect until you reboot the system.
44 Sun Enterprise 250 Server Owner's Guide • June 1998