This blog post is not related to database upgrades and migrations. But still I think it is very useful for many customers operating on modern Linux systems.
Support just published an ALERT strongly recommending to disable Transparent Hugepages on Linux systems. And the below information does not apply to RAC systems only but also to single instance environments.
Which Linux Distrubutions/Kernels are affected?
- RHEL6 and RHEL7
- OL6 and OL7
- UEK2 Kernels
What are the Issues?
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.
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. See MOS Note:361323.1 for additional information on HugePages.
As far as I see you’ll have to reboot the server in order to disable Transparent Hugepages – the default is usually ALWAYS.
- MOS Note: 1557478.1
ALERT: Disable Transparent HugePages on SLES11, RHEL6, RHEL7, OL6, OL7 and UEK2 Kernels
- MOS Note 2066217.1
Oracle Linux 7 – How to disable Transparent HugePages for RHCK kernel?
- MOS Note; 361323.1
HugePages on Linux: What It Is… and What It Is Not…