Hardware Watchdog Mechanism; Four Levels Of Diagnostics - Sun Microsystems Enterprise 250 Owner's Manual

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.

Four Levels of Diagnostics

For enhanced serviceability and availability, the system provides four different levels
of diagnostic testing: power-on self-test (POST), OpenBoot diagnostics (OBDiag),
TM TM TM
SunVTS , and Solstice SyMON .
POST and OBDiag are firmware-resident diagnostics that can run even if the server
is unable to boot the operating system. Application-level diagnostics, such as
SunVTS and Solstice SyMON, offer additional troubleshooting capabilities once the
operating system is running.
POST diagnostics provide a quick but thorough check of the most basic hardware
functions of the system. For more information about POST, see "About Power-On
Self-Test (POST) Diagnostics" on page 235 and "How to Use POST Diagnostics" on
page 236.
OBDiag provides a more comprehensive test of the system, including external
interfaces. OBDiag is described in "About OpenBoot Diagnostics (OBDiag)" on page
239 and "How to Use OpenBoot Diagnostics (OBDiag)" on page 248.
Sun Enterprise 250 Server Owner's Guide ♦ Revision A, June 1998
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