Unformatted text preview: a warehouse is organized
around a specific subject area from the perspective of the end user (such as
customers, products, or accounts) to rapidly provide information relating to this
specific area. This is in contrast to most operational database systems in which
data is organized around the specific functions or activities of an application (such
as, inventory control, pay-roll, or invoicing) to enable efficient access, retrieval,
2. Integrated. Data residing in many different operational database systems is
often inconsistent in terms of coding and formats. On the other hand, even when
the data in a data warehouse is sourced from multiple database systems (or
multiple data sources), it is ensured during the data clearing process that all data in
the data warehouse is consistent and uniform, thereby eliminating the issues of
data incompatibility and portability.
Time-variant. In operational database systems, data is accurate at the
moment of access only. However, all data in a data warehouse is accurate at a
specific point-in-time and can be kept over a long time period. Due to this feature,
the data in a data warehouse provides a historical perspective.
4. Non-volatile. In operational database systems, data is continuously updated
on a record-by-record basis. On the other hand, in a data warehouse, data is
periodically loaded en mass and accessed later. It is never updated and retains its
Thus, data in a data warehouse is static, not dynamic. The only
operations that occur in data warehouse applications are the initial loading of data,
access of data, and refresh of data. Due to this reason, the physical design of a
data warehouse optimizes the access of data, rather than focusing on the
requirements of data update and delete processing.
Need for a Data Warehouse
A data warehouse is typically needed in an organization in one or more of the
The organization has several operational database systems, but there is no
mechanism to present a holistic view of the entire gamut of information from the
data stored in these databases.
2. Same data is present on different operational database systems in different
departments about which users are not aware and/or different systems are giving
different answers to the same business questions. 3.
Decision makers and policy planners are not able to obtain easily
decipherable, timely, and comprehensible information due to the non-availabilit...
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This document was uploaded on 04/07/2014.
- Spring '14