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Data warehouses may hold large amounts of information, sometimes in smaller logical units called Data marts. Often the schemas of data marts are stored in what are known as " star schemas", or dimensional modeling form; however there is no industry standard requiring that the schemas of data marts be in any particular form. There is, in fact, some controversy about the most useful form of data mart schemas.

Conventional database systems use highly normalized data formats to ensure consistency of data and minimal use of space. However this often means that transactions and queries against a fully normalized database perform slowly. Data warehouses often use a more de-normalized (relaxed) format. This speeds up queries, and has the additional benefit that the schema will be more intuitive to non-administrative users as they are exploring it. For example, rather than having a single record in a table contain customer information, that information may be replicated across a whole series of tables.

Data being pushed into a warehouse is usually "staged". Data staging occurs when a periodic process reads data from sources (often a business's primary OLTPOLTP is a computing acronym for on-line transaction processing. This is a class of program that facilitates and manages transaction-oriented applications, typically for data entry and retrieval in a number of industries, including banking, airlines, mailo databases), scrubs this information for quality, de-normalizes it, and writes it into the warehouse. This process is usually carried out with an ETL tool.

Data warehouses are usually accessed (queried) via "data marts", which are purpose-specific access points to or sub-sets of the warehouse. Data marts are designed to answer the probable queries of a given kind of user.

Normally a data warehouse does not store current information on an individual business activity. It is often used for collective processing for all business units across a corporation.

Computing in data warehouses is often referred to as Online Analytical Processing ( OLAP), in contrast to Online Transaction Processing ( OLTPOLTP is a computing acronym for on-line transaction processing. This is a class of program that facilitates and manages transaction-oriented applications, typically for data entry and retrieval in a number of industries, including banking, airlines, mailo) -- used for normal business activities. Data from Enterprise resource planningEnterprise resource planning as a term, derives from material resource planning. Enterprise resource planning systems (ERP) are management information systems that integrate and automate many of the business practices associated with the operations or pro (ERP) systems and other related business software systems is imported into data warehouses periodically for further processing.

1 Companies providing Datawarehousing Solutions:

• SaksoftSaksoft is a Indian Business Consulting company, primarily based in the United States, India, Singapore, London and Frankfurt. It is a member of the Sak family of companies. Saksoft is a specialized provider of business intelligence, business performance