I have a Dell PowerEdge 2900 that has been running 24/7 for nearly 18 months that rebooted unexpectedly today. OMSA doesn't show any errors, except that the RAID controller firmware is out of date, but that's been the case for months now.
Unfortunately I don't have a dump file to look through. OMSA reports all 4 DIMMs are "OK" as well as both CPUs. Both PSUs show OK. Temp shows 20 C. Voltage readings all show "Good".
I'm at a loss at this point, and this is a production server.