Data warehousing Concept:-part1

1-  A data warehouse is a relational database that is designed for query and analysis rather than for transaction processing. It usually contains historical data derived from transaction data.

      
2-  Data warehousing is subject-oriented, integrated, time-variant, and non-volatile collection of data in support of management’s decision-making process.

     3-   A data warehouse is data management and data analysis.

   4- Goal: is to integrate enterprise wide corporate data into a single repository from which users can easily  run queries.

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 What is data warehousing?

     Subject- Oriented à DWH is organized around the major subjects of the enterprise..rather than the major application areas.This is reflected in the need to store decision-support data rather than application-oriented data. For example, to learn more about your company’s sales data,you can build a warehouse that concentrates on sales.

     Non Volatile à Nonvolatile means that,once entered into the warehouse, data should not change.This is logical because the purpose of a warehouse is to enable you to analyze what has occurred.

     Integrated à  Integration is closely related to subject orientation. Data warehouses must put data from disparate sources into a consistent format. They must resolve such problems as naming conflicts and inconsistencies among units of measure. When they achieve this, they are said to be integrated.

      Time Variant à In order to discover trends in business, analysts need large amounts of data. This is very much in contrast to online transaction processing (OLTP) systems, where performance requirements demand that historical data be moved to an archive. A data warehouse’s focus on change over time is what is meant by the term time variant.