This is a simple symptom-cause-solution blog entry only. I hope these blogs will help fellow administrators.
On Red Hat Enterprise Linux 4 (and possibly other flavours and versions) all weblogic processes are disappearing and there are no errors in the server logs. Upon closer inspection the processes are being killed by the OS. The Linux "dmesg" command shows log messages like:
Out of Memory: Killed process 22043
The processes are using up too much low- (under 640k) or high-memory and the Linux OOM-Killer is killing the processes.
Either disable OOM-killer, or make it work more aggresively.
To disable, run this command:
echo "0" > /proc/sys/vm/oom-kill
To make more aggressive:
echo "250" > /proc/sys/vm/lower_zone_protection