Data virtualisation can simplify data access and improve agility. Three uses of virtual data sources are: 1) Merger and Acquisition: Due to merger of data warehouses, OLTP systems are changed which causes the ETL jobs to break. This situation can be avoided by introducing virtual data sources between source OLTP systems and the data warehouse or between data warehouses and data marts, 2) Stabilizing data warehouse ETL processing, 3) Simplifying self-service data preparation for business users to access data across multiple data sources. In conclusion, virtual data sources are useful in practice because of its ability to de-couple physical data sources from ETL processing improve design and introduce governance. Read more at: http://www.datavirtualizationblog.com/overlooked-capability-data-virtualisation/