This post covers steps to configure YUM so that you can install missing RPM (RPMs required for Oracle Database and Fusion Middleware).
1. Identify your Oracle Enterprise Linux version from enterprise-release file
You should see entry like
Enterprise Linux Enterprise Linux Server release 5.5 (Carthage)
Output above represents that version of Linux is 5.5
2. Next task is to download yum repository configuration file from Oracle Public Yum Server.
# cd /etc/yum.repos.d
# wget http://public-yum.oracle.com/public-yum-el5.repo
3. Enable yum for 5.5 (as our linux version is 5.5) in file /etc/yum.repos.d/public-yum-el5.repo by changing enabled from 0 to 1. Enable same as per your OEL version
name=Enterprise Linux $releasever Update 5 installation media copy ($basearch)
4. Install packages in Oracle Linux as shown below
yum install [package_name]