The software described in this documentation is either in Extended Support or Sustaining Support. See https://www.oracle.com/us/support/library/enterprise-linux-support-policies-069172.pdf for more information.
Oracle recommends that you upgrade the software described by this documentation as soon as possible.

2.7 Switching CentOS or Scientific Linux Systems to Use the Oracle Linux Yum Server

You can use the centos2ol.sh script to convert CentOS 5 and 6 or Scientific Linux 5 and 6 systems to Oracle Linux. The script configures yum to use the Oracle Linux yum server and installs a few additional packages that are required. There is no need to reboot the system.

To perform the switch to Oracle Linux, run the following commands as root:

# curl -O https://linux.oracle.com/switch/centos2ol.sh
# sh centos2ol.sh

For more information, see https://linux.oracle.com/switch/centos/.