The yum repository should be configured in order to download and install any oracle library, if you don't want to search for the libraries one by one. To configure library you have to:

1. Download the repository
2. Configure the GPG Key
3. Choose your package

The repository can be downloaded used the following syntax:

wget http://yum.oracle.com/public-yum-release.repo

wget http://yum.oracle.com/public-yum-ol6.repo

ol6 = Oracle Linux 6

The GPG key is needed and can be downloaded from:

cd /etc/pki/rpm-gpg/
wget http://public-yum.oracle.com/RPM-GPG-KEY-oracle-ol7

Older versions
http://public-yum.oracle.com/RPM-GPG-KEY-oracle-ol6

http://public-yum.oracle.com/RPM-GPG-KEY-oracle-el5

http://public-yum.oracle.com/RPM-GPG-KEY-oracle-el4

Oracle Libraries sometimes can come hard to find. That is why Oracle created the pre-install packages, which contains the entire set of libraries needed. Currently there are the following preinstall packages:

yum -y install oracle-rdbms-server-11gR2-preinstall
yum -y install oracle-rdbms-server-12cR1-preinstall
yum -y install oracle-database-server-12cR2-preinstall