The currently accepted definition of a data mart is simply a subject- or applicationspecific
data warehouse, usually implemented within a department. Typically, these
data marts are built for performance and may include a large number of summary
tables. Data marts were initially thought of as being small, since not all the detail
data for a department or data from other departments need be loaded in the mart.
However, some marts get quite large as they incorporate data from outside sources
(sometimes purchased) that isn??™t relevant in other parts of the business.
In some organizations, data marts are deployed to meet specific project goals with
models optimized for performance for that particular project. Such data marts are
retired when the project is completed and the hardware is reused for other projects.
As the analysis requirements for a business change, the topology of any particular
data warehouse is subject to evolution over time, so developers must be aware of this
possibility.
Increasing focus on cost savings, manageability, and compliance are leading many to
reexamine the wisdom of having a large number of physically separate data marts.
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