How to trace the issue? Why server hung and restart?

I saw Exadata Database server hang .... and last log
/var/log/messages file:

Aug  2 09:14:09 exadb03 snmptrapd[31304]: No access configuration - dropping trap.
Aug  2 09:21:00 exadb03 auditd[6123]: Audit daemon rotating log files
Aug  2 10:07:22 exadb03 syslogd 1.4.1: restart.
Aug  2 10:07:22 exadb03 kernel: klogd 1.4.1, log source = /proc/kmsg started.


[root@exadb03 exadb03]# last
root     pts/0        10.10.10.129      Tue Aug  2 10:07 - 10:37  (00:29)
reboot   system boot  2.6.18-194.3.1.0 Tue Aug  2 10:06          (01:58)
oracle   pts/1        exadb01.domain Tue Aug  2 02:33 - 02:33  (00:00)


[root@exadb03 log]#  ipmitool sel list
.
.
.
  f8 | 08/02/2011 | 00:28:54 | System ACPI Power State #0x26 | S0/G0: working | Asserted
  f9 | 08/02/2011 | 10:03:19 | System Boot Initiated | Initiated by warm reset | Asserted
  fa | 08/02/2011 | 10:03:19 | System Firmware Progress | Memory initialization | Asserted
  fb | 08/02/2011 | 10:03:19 | System Firmware Progress | Primary CPU initialization | Asserted