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Data Warehousing

Data warehousing defines strategies for making this data more accessible. Every day, organizations capture data that is essentially unavailable for use because there is no way to conveniently access, manipulate, and present it. Billions of bytes of data are essentially “locked up” on computer stems throughout an organization.

A data warehouse can be thought of as a three-tier system in which a middle system provides usable data in a secure way to end users. On either side of this middle system are the end users and the back-end data stores.
Industry analysts and system vendors long ago recognized that there are two types of information systems:

1. Operational systems
2. Informational systems

The important difference between the two system for the purposes of this discussion is that operational systems deal with a specific set of data, such as the inventory, while information systems are concerned with extracting useful information from a viety  related information sources. Informational systems access and use data from the following information sources:

• Legacy data systems
• External data systems
• Operational data systems

The data warehouse can be thought of as a system that holds summary information from legacy, operational or external data sources. Staging systems store only the latest information for read only purposes. All data updates take place on operational systems, not on the staging system.

More reading, Please visit:

http://www.linktionary.com/datawarehouse.html

http://www.dw-institute.com

http://www.idwa.org

http://www.cait.wustl.edu/infosys/infosys.html