Supposing that you have a clear installation of a Centos 6.3 and you want to upgrade it to Centos 6.4, you have to do two steps to complete this process. The first step is to run a yum update command:
The second step is to remove the deprecated matahari, as proposed from Centos 6.4 Release Notes
To ensure that you have successfully upgraded to 6.4 run the command:
if Centos Relsease 6.4 (Final) is the content of the /etc/redhat-release file then you can continue to the next step:
yum erase matahari*
If it’s a clean installation, possibly there is no remains of matahari packages on the system.