in oel 5.7 under the system tab >>admin.. there are links for users&groups, printing, server setting and a bunch more, on oel 6.3 the only items that show are
add/remove software, software update, uln registrations... where did everthing else go ???
Whatever you have done to install a graphical user desktop (Gnome) under OL 6.3 was obviously missing the package group that installs the software you are missing. You are probably missing the "Graphical Administration Tools" package.
Perhaps you can try the following command:
yum groupinstall "Graphical Administration Tools"
Btw, this post rather belongs to the "Oracle Linux" forum.