The systems that contain operational data--the data that runs the daily transactions of your business--contain information that is useful to business analysts. For example, analysts can use information about which products were sold in which regions at which time of year to look for anomalies or to project future sales. However, there are several problems if analysts access the operational data directly:
Data warehousing solves these problems. In data warehousing, you create stores of informational data--data that is extracted from the operational data and then transformed for end- user decision making. For example, a data warehousing tool might copy all the sales data from the operational database, perform calculations to summarize the data, and write the summarized data to a separate database from the operational data. End-users can query the separate database (the warehouse) without impacting the operational databases.