Oracle recently announced the availabilty of Unbreakable Enterprise Kernel (UEK) Release 4 for Oracle Linux 6 and Oracle Linux 7 Here

Do the following to upgrade existing systems to UEK4:

OEL6 :

mv public-yum-ol6.repo public-yum-ol6.repo.old
wget http://public-yum.oracle.com/public-yum-ol6.repo
vi public-yum-ol6.repo

In the section [ol6_UEKR4] change enabled=0 to enabled=1 and then run yum update and reboot

yum update
reboot

OEL7 is the same except for the first two steps where you download the OEL7 public yum details instead

mv public-yum-ol6.repo public-yum-ol7.repo.old
wget http://public-yum.oracle.com/public-yum-ol7.repo