In September 2010, Oracle announced the new Unbreakable Enterprise Kernel (UEK) for Oracle Linux as a recommended kernel for deployment with Oracle Linux 5. Beginning with Oracle Linux 5.5, you could choose to use either the Red Hat Compatible Kernel or the UEK. In Oracle Linux 5.6, the UEK became the default kernel.

The prime motivation for creating the UEK was to provide a modern, high performance Linux kernel for the Exadata and Exalogic engineered systems. The kernel needed to scale as the number of CPUs, memory and InfiniBand connects was increased.

Oracle tests the UEK intensively with demanding Oracle workloads, and recommends the UEK for Oracle deployments and all other enterprise deployments. Oracle is committed to offering compatibility with Red Hat, and continues to release and support the Red Hat Compatible Kernel as part of Oracle Linux for customers that require strict RHEL compatibility. Under the Oracle Linux Support Program, customers can receive full support for Oracle Linux running with either kernel.

Oracle releases new versions of the UEK every 12-18 months. The latest version of the UEK receives quarterly patch updates including drivers for new hardware support, bug fixes, and critical security patches. Oracle also provides critical security patches for previous versions of the UEK. These patches are available as new installable kernels and, with the exception of device driver updates, as Ksplice patches.

Using the UEK instead of the Red Hat Compatible Kernel changes only the operating system kernel. There are no changes to any libraries, APIs, or any user-space applications Existing applications run unchanged regardless of which kernel you use. Using a different kernel does not change system libraries such as glibc. The version of glibc in Oracle Linux 6 remains the same, regardless of the kernel version.