I think Dipanjan is spot-on. Federated access is the solution. There is a whole bunch of good documents on IBM site. Federated Systems Guide might suit you well.
Besides, you can also check out the following link as well. This will outline how federation engine work.
http://www-106.ibm.com/developerwork...0304lurie.html
There is a utility called "Information Integrator" from IBM. Please check the IBM site for more information.
Hope this helps.