Data Warehousing: Issues and Impact on Information Systems

Abstract

The fundamental role of a data warehouse is to provide data for supporting decision-making process. These kinds of applications for which data warehouses are used have existed for some time (e.g.. executive information system). Data warehouses have added new benefits to them by improving and expanding the scope, accuracy, and accessibility of data. Data in warehousing environment is multidimensional and stored in a database. We can simply say that data warehousing is a process not a product for assembling and managing data from various sources for the purpose of gaining a single detailed view of part or all of a business. The data warehouse concept has changed the nature of decision support .The

warehouse is the link between the application and the data (which was scattered in

separate databases but is now unified) .

Data warehouses differ from operational databases in that they are:

Subject oriented: Data are organized by how users refer to it.

Integrated: Inconsistencies are removed iri both nomenclature and conflicting information, that is, the dataare clean. Time variant Data are time series, not current status. Data warehouse often

• supports analysis of trend over time and comparison of current vs. historical data. Non volatile: read only data, data are not updated by users.

Summarized: Operational data are aggregated, when appropriate into decision

-usable form.

Larger: Keeping a time series implies that much more data is retained.

Not Normalized: Data can be redundant

Impact: Operational data ("Legacy System") plus external data as needed.