A Data Warehouse is a collection of corporate information that information is derived from operational systems and external data sources. A Data Warehouse is designed to support data consolidation, analysis and reporting at different aggregate levels. In a Data Warehouse data from many heterogeneous sources is extracted into a single area and transformed according to the decision support system needs and stored into the warehouse. Data Warehouse includes development of systems to extract data from operating systems plus installation of a warehouse database system that provides managers flexible access to the data.