Execution of yum leads to "Warning: RPMDB altered outside of yum."

Issue

• While installing/updating a package using yum, the following warning message is observed:

  # yum install <package name>
  Loaded plugins: rhnplugin
  Setting up Install Process
  Resolving Dependencies
  --> Running transaction check
  ...
  Running rpm_check_debug
  Running Transaction Test
  Transaction Test Succeeded
  Running Transaction
  Warning: RPMDB altered outside of yum.         <<<<<<<<<<< here
  ...
  

• Other commands, such as yum history, could show that the RPM database had been altered outside of yum a lot:

  ...
  Warning: RPMDB altered outside of yum.
  ** Found 3578 pre-existing rpmdb problem(s), 'yum check' output follows:
  ...