A DW or data warehouse is the database which is used for reporting. The information is offloaded from the operational system for the reporting. Information or data might pass via the operational information or data store for extra operations before it is utilized in the data ware house for the reporting purpose. The data ware house maintains its functions in three levels or layers such as access, integration and staging. The staging is used in order store the raw information or data for the use by the developers (support and analysis). The integration layer is generally used in order to integrate the information and to have the level of the abstraction from the users. The next layer is the access which is used for getting data for the users.
The meaning of the data warehouse mainly focuses on the data storage or storage memory. The main source of the information or data is cleaned, catalogued, transformed and made available for use by the managers and other company or business professionals for online analytical; processing, data mining, decision support and market research.
But, the means to analyze and retrieve data, to transform, load and extract data, and to manage the data dictionary are also considered important elements of the data warehousing system. Several references to the data warehousing employ this broader context. Therefore, an expanded definition for the data warehousing comprises the business intelligence tools, the tools which is used to extract, transform and load information, into the repository, and tools used in order to retrieve and manage the data.
Architecture of the data warehouse layers is as follows