How to install GUI in Oracle Linux 7?

root@oraclelinux7:/# yum grouplist
Loaded plugins: ulninfo
There is no installed groups file.
Maybe run: yum groups mark convert (see man yum)
Available Environment Groups:
   Minimal Install
   Infrastructure Server
   File and Print Server
   Cinnamon Desktop
   MATE Desktop
   Basic Web Server
   Virtualization Host
   Server with GUI
Available Groups:
   Additional Development
   Backup Client
   Backup Server
   Base
   CIFS file server
   Compatibility libraries
   Console internet tools
   Debugging Tools
   Desktop
   Desktop Debugging and Performance Tools
   Desktop Platform
   Desktop Platform Development
   Development tools
   Dial-up Networking Support
   Directory Client
   Directory Server
   E-mail server
   Eclipse
   Educational Software
   Electronic Lab
   Emacs
   FCoE Storage Client
   FTP server
   Fedora Packager
   Fonts
   General Purpose Desktop
   Graphical Administration Tools
   Graphics Creation Tools
   Hardware monitoring utilities
   Haskell
   Infiniband Support
   Input Methods
   Internet Applications
   Internet Browser
   Java Platform
   KDE Desktop
   Large Systems Performance
   Legacy UNIX compatibility
   Legacy X Window System compatibility
   Mainframe Access
   Messaging Client Support
   Messaging Server Support
   Milkymist
   MySQL Database client
   MySQL Database server
   NFS file server
   Network Infrastructure Server
   Network Storage Server
   Network file system client
   Networking Tools
   Office Suite and Productivity
   PHP Support
   Performance Tools
   Perl Support
   PostgreSQL Database client
   PostgreSQL Database server
   Print Server
   Printing client
   Remote Desktop Clients
   SNMP Support
   Scientific support
   Security Tools
   Server Platform
   Server Platform Development
   Smart card support
   Storage Availability Tools
   System Management
   System administration tools
   TeX support
   Technical Writing
   TurboGears application framework
   Virtualization
   Virtualization Client
   Virtualization Platform
   Virtualization Tools
   Web Server
   Web Servlet Engine
   Web-Based Enterprise Management
   X Window System
   Xfce
   iSCSI Storage Client
Done
root@oraclelinux7:/ yum grouplist | grep GUI
There is no installed groups file.
Maybe run: yum groups mark convert (see man yum)
   Server with GUI
root@oraclelinux7:/ yum groupinstall "Server with GUI"

root@oraclelinux7:~# runlevel
N 3
root@oraclelinux7:~# ll  /etc/systemd/system/
total 20
drwxr-xr-x. 17 root root 4096 Feb  7 20:10 ./
drwxr-xr-x.  4 root root 4096 Feb  7 20:04 ../
drwxr-xr-x.  2 root root   30 Jul 24  2014 basic.target.wants/
drwxr-xr-x   2 root root   30 Feb  7 20:05 bluetooth.target.wants/
lrwxrwxrwx   1 root root   41 Feb  7 20:05 dbus-org.bluez.service -> /usr/lib/systemd/system/bluetooth.service
lrwxrwxrwx.  1 root root   44 Jul 24  2014 dbus-org.freedesktop.Avahi.service -> /usr/lib/systemd/system/avahi-daemon.service
lrwxrwxrwx   1 root root   44 Feb  7 20:10 dbus-org.freedesktop.ModemManager1.service -> /usr/lib/systemd/system/ModemManager.service
lrwxrwxrwx.  1 root root   46 Jul 24  2014 dbus-org.freedesktop.NetworkManager.service -> /usr/lib/systemd/system/NetworkManager.service
lrwxrwxrwx.  1 root root   57 Jul 24  2014 dbus-org.freedesktop.nm-dispatcher.service -> /usr/lib/systemd/system/NetworkManager-dispatcher.service
lrwxrwxrwx.  1 root root   37 Jul 24  2014 default.target -> /lib/systemd/system/multi-user.target
drwxr-xr-x.  2 root root   85 Jul 24  2014 default.target.wants/
drwxr-xr-x   2 root root   37 Feb  7 20:10 dev-virtio\x2dports-org.qemu.guest_agent.0.device.wants/
lrwxrwxrwx   1 root root   35 Feb  7 20:08 display-manager.service -> /usr/lib/systemd/system/gdm.service
drwxr-xr-x.  2 root root   31 Jul 24  2014 getty.target.wants/
drwxr-xr-x   2 root root  107 Feb  7 20:08 graphical.target.wants/
drwxr-xr-x.  2 root root 4096 Feb  7 20:10 multi-user.target.wants/
drwxr-xr-x   2 root root   25 Feb  7 20:08 printer.target.wants/
drwxr-xr-x   2 root root   30 Jul 18  2017 remote-fs.target.wants/
drwxr-xr-x.  2 root root 4096 Feb  7 20:08 sockets.target.wants/
drwxr-xr-x   2 root root   35 Feb  7 20:10 spice-vdagentd.target.wants/
drwxr-xr-x.  2 root root 4096 Feb  7 20:06 sysinit.target.wants/
drwxr-xr-x.  2 root root   43 Jul 24  2014 system-update.target.wants/
drwxr-xr-x   2 root root   33 Feb  7 20:06 timers.target.wants/
drwxr-xr-x   2 root root   28 Feb  7 20:08 vmtoolsd.service.requires/
root@oraclelinux7:~# 
root@oraclelinux7:~# ls -ltr /lib/systemd/system/graphical.target
-rw-r--r-- 1 root root 558 Feb  1 07:33 /lib/systemd/system/graphical.target
root@oraclelinux7:~# 
root@oraclelinux7:~# rm /etc/systemd/system/default.target
root@oraclelinux7:~# ln -n /lib/systemd/system/graphical.target /etc/systemd/system/default.target
root@oraclelinux7:~# reboot