This is important as unfortunately Centos may designate a package obsolete and the replacement breaks everything (eg. you have a config file and the new replacement is not at all compatible with it and it breaks your application).
This is where disabling obsoletes comes into play, it can be done from yum but it doesn't work at the time I find.
yum --setopt=obsoletes=0 install someappHowever I find it still installs the new app and not the one you ask for until the second run which is kind of pointless. I recommend just turning this feature off from yum.conf