How to Fix “Warning: RPMDB altered outside of yum.”

Symptom:

When i try to install the packages or software using the yum command, the following error or warning message appeared:

Warning: RPMDB altered outside of yum.
Example :

..
..
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
Warning: RPMDB altered outside of yum.
..
..
This means some application has altered the rpm database (installed or removed a package) without going through the Yum APIs. To avoid this, it’s recommended to update, install or remove RPM packages using yum command, instead of ” rpm -e” or “rpm -i” or “rpm -ivh” or “rpm -Uvh”.
To fix this, just run this command :

[root@centos6 ~]# yum clean all
Loaded plugins: fastestmirror
Cleaning repos: CentOS6.2-Repository
Cleaning up Everything
Cleaning up list of fastest mirrors