Data Warehousing

Abbreviated DW, a collection of data designed to support management decision making. Data warehouses contain a wide variety of data that present a coherent picture of business conditions at a single point in time.

“A Decision Support DB that is maintained separately from the organisation's operational Databases”.

What is a Data Warehouse?

A data warehouse is something you do, not something you buy. A successful data warehouse does not have an end. Regardless of the methodology, warehousing environments must be built incrementally through projects that are managed under the umbrella of a data-warehousing program. That program will be sponsored and supported at the Department of Information Technology.

Most of the benefits of the data warehouse will not be realized in the first delivery. The first project will be the foundation for the next, which will in turn form the foundation for the next. Data warehousing at the enterprise level is a long-term strategy, not a short-term fix. Its cost and value should be evaluated across a time span sufficient to provide us with a realistic picture of its cost-to-value ratio.

A DW is:

·        Subject-oriented: The warehouse is organized around the major subjects of the enterprise (e.g. customers, products, and sales) rather than the major application areas (e.g. customer invoicing, stock control, and product sales).

·        Integrated: The data warehouse integrates corporate application-oriented data from different source systems, which often includes data that is inconsistent. The integrated data source must be made consistent to present a unified view of the data to the users.

·        Time-variant: Data in the warehouse is only accurate and valid at some point in time or over some time interval. also shown in the extended time that the data is held, the implicit or explicit association of time with all data, and the fact that the data represents a series of snapshots.Warehouse data represent the time, and queries are based on time range.

·        Non-volatile: Data in the warehouse is not updated in real-time but is refreshed from operational systems on a regular basis. New data is always added as a supplement to the database, rather than a replacement.

Collection of data that is used primarily in organizational decision making.

Development of a data warehouse includes development of systems to extract data from operating systems plus installation of a warehouse database system that provides managers flexible access to the data.

The term data warehousing generally refers to the combination of many different databases across an entire enterprise. Contrast with data mart.

Benefits of DW:

·        Potential high returns on investment

·        Competitive advantage

·        Increased productivity of corporate decision-makers