A database designed to support decision making in an organization. Data from the production databases are copied to the data warehouse so that queries can be performed without disturbing the performance or the stability of the production systems.Data MartsData warehouses can become enormous with hundreds of gigabytes of transactions. As a result, subsets, known as "data marts," are often created for just one department or product line.Updated at the End of a PeriodData warehouses are generally batch updated at the end of the day, week or some period. Its contents are typically historical and static and may also contain numerous summaries.Operational Data StoresThe data warehouse is structured to support a variety of analyses, including elaborate queries on large amounts of data that can require extensive searching. When databases are set up for queries on daily transactions, they are often called "operational data stores" rather than data warehouses (see ODS). See OLAP, decision support system, EIS and BI software.