Note: This ONLY applies to the new feature Transparent HugePages, Oracle highly recommends the use of standard HugePages that were recommended for previous releases of Linux
Transparent HugePages are implemented and enabled (default) in an attempt to improve the memory management.
Because Transparent HugePages are known to cause unexpected node reboots and performance problems with RAC, Oracle strongly advises to disable the use of Transparent HugePages. In addition, Transparent Hugepages may cause problems even in a single-instance database environment with unexpected performance problems or delays. As such, Oracle recommends disabling Transparent HugePages on all Database servers running Oracle.
Symptoms :
Node reboots.
The ocssd.log may show some of the threads are blocked (but this does not show all the time):
2013-05-01 14:30:45.255: [ CSSD][224204544]clssscMonitorThreads clssnmvKillBlockThread not scheduled for 7500 msecs
2013-05-01 14:30:46.945: [ CSSD][224204544]clssscMonitorThreads clssnmvWorkerThread not scheduled for 8030 msecs
How to Disable :
Add the following to the kernel boot line in /etc/grub.conf (a symlink to /boot/grub/grub.conf) and reboot the server (this is the preferred method):
transparent_hugepage=never