Define a Warehouse
a data warehouse is a federated repository for all your information that an enterprise’s various business methods collect. The repository is actual or logical.
Information warehousing emphasizes the capture of information from diverse sources for useful analysis and access, but does not typically begin with the point-of-view for the end user just who may require use of specialized, occasionally neighborhood databases. The second idea is known as the info mart.
There are two ways to information warehousing, top down and bottom up. The most notable down method spins down information marts for certain categories of users following the complete information warehouse is created. The underside up method develops the information marts initially and then integrates them into just one, all-encompassing information warehouse.
Typically, a data warehouse is housed on an enterprise mainframe server or increasingly, in the cloud. Data from various online transaction processing (OLTP) applications and other sources is selectively extracted for use by analytical applications and user queries.