Data warehouses

Usually, the information within an organization is kept in one of two forms—in an operational system or in an analytical system—both of which have very different purposes. Although the purpose of an operational system, which is also known as an OLTP system, is to support the execution of a business process, the purpose of an analytic system or data warehouse is to help with the measurement of a business process and business decision-making. OLTP systems are based on small, high-performance transactions consisting of INSERT, DELETE, UPDATE, and SELECT statements, while a data warehouse is based on large and complex queries of aggregated data. The degree of normalization is another main difference between these systems: while an OLTP system will usually be in the third normal form, a data warehouse will use a denormalized dimensional model called a star schema. The third normal form used by OLTP systems helps with data integrity and data redundancy problems...