This page describes the process of how to install Oracle's Unbreakable Enterprise Kernel (UEK or kernel-uek) on Centos or RHEL.
Why use UEK?
Why would you want to install the Oracle UEK on CentOS or RHEL? If you're planning to run Oracle RAC on CentOS/RHEL 6.3 virtual machine (under RHEV/oVirt), you're gonna need it!* Since RHEL v6.1 Oracle are no longer providing oracleasm drivers for the newer kernels. They have instead decided to bundle the oracleasm drivers into their Unbreakable Enterprise Kernel. This actually makes installing Oracle RAC a little easier as you don't have to go searching for the oracleasm driver specific to your kernel! Just do a yum install! Yes, even on CentOS or RHEL!