The following packages (a.k.a RPMs) are required to setup X Windows on Linux, specifically Oracle Enterprise Linux (OEL) with the UEK kernel. It is tested successfully on Oracle Linux 7 update 3 for x86_64. These packages also install KDE as the default desktop environment on this Linux operating system.
Login as root and run the yum install package command for each such package below.
yum install vnc
yum install vnc-server
yum install xterm
yum groupinstall "X Window System"
yum install kdebase
yum install gnome-terminal
yum groupinstall "KDE"