It is often the case in large enterprises that multiple data marts are deployed, along with a central enterprise data warehouse acting as a system of record. While these data marts serve the requirements of the departments or divisions that implement them, a frequent requirement is to merge data across these implementations. While this can be done by replicating the data across systems, this is an expensive and inflexible option. A preferred solution is to use federated technology that will support queries across systems. This is what Netezza Data Virtualizer does. It also supports other use cases but this will be the primary one for most companies.