There is no yum repository in Oracle Linux after installation, so it’s necessary to set it in order to update the system with yum command.
Oracle provides public yum server and we can use it for free to set.
⇒ Public Yum Server : http://public-yum.oracle.com/
### Download repository file
[root@testos ~]# cd /etc/yum.repos.d/
### Oracle Linux 7
[root@testos ~]# wget http://public-yum.oracle.com/public-yum-ol7.repo
### Oracle Linux 6
[root@testos ~]# wget http://public-yum.oracle.com/public-yum-ol6.repo