I am new to Linux servers and have one that freezes on average about once every 6-12 days.

Dell PE6400 with RedHat AS 2.4.21.
Oracle 10g server with several db instances.
One external Sony SAIT3 tape drive.
ARCserve 11.1 backup software.

It usually freezes at night but sometimes during the day. Only a hard restart will allow it to recover. There seems to be no data loss. The oracle logs show no problems for the time periods in question. I have found some message logs and others in /var/logs/ but they show nothing indicating a problem, there are simply no entries for the time period of the freeze.
I suspect that there may be other logs somewhere that could help me identify the problem but have not found them yet. I also suspect that there could be a driver or compatibility issue with something but am not familiar enough with Linux to know how to go about identifying it.
Any suggestions or leads to resources on how to identify the problem would be greatly appreciated.
Thanks.