Setting Hugepages on Exadata

Get the script for MOS support

Oracle Linux: Shell Script to Calculate Values Recommended Linux HugePages / HugeTLB Configuration (Doc ID 401749.1)

Start all DB instances on the server

Now run the script from MOS support. It will give you a recommended value. Now configure hugepages for Linux

You need to be root to do this. If this is the first time you are configuring you might need to reboot the server.

Note: Huge pages value should be greater than or equal to all the SGA's combined on the server.

You can check the hugepages config using

$ grep Huge /proc/meminfo

Now run the following as root and enter the recommended value you got from the script.

# vi /etc/sysctl.conf

vm.nr_hugepages=55425

Save it and quit.

Now run

# sysctl -p

Now verify the changes using

$ grep Huge /proc/meminfo

If you dont see any changes you will need to reboot.

While modifying this also verify hard limit and soft limit in the following file

/etc/security/limits.conf

oracle    soft     memlock 237674430
oracle    hard     memlock 237674430

Now set the following in individual db instances

Note: It is a good idea to set value to TRUE because DB will fail to start if you configure only and enough memory is not configured in Huge pages.

We have USE_LARGE_PAGES parameter on the databases. Setting this parameter will improve memory management on the database.

We have 3 values for the above parameter TRUE, FALSE and ONLY

If you set to TRUE, DB will use huge pages and will be started even if hugepages values is less than SGA of database.
If you set to FALSE, DB will not use huge pages
If you set to ONLY, DB will fail to start if huge pages cannot be used for entire SGA of database.