Datamart and Datawarehouse development
A data warehouse
is the main repository of an organization's historical data, its corporate
memory. It contains the raw material for management's decision support system.
The critical factor leading to the use of a data warehouse is that a data
analyst can perform complex queries and analysis, such as data mining, on
the information without slowing down the operational systems.
A data mart (DM) is a specialized version of a data warehouse (DW). Like data
warehouses, data marts contain a snapshot of operational data that helps business
people to strategize based on analyses of past trends and experiences. The
key difference is that the creation of a data mart is predicated on a specific,
predefined need for a certain grouping and configuration of select data. A
data mart configuration emphasizes easy access to relevant information.
In practice, the terms data mart and data warehouse each tend to imply the
presence of the other in some form. However, most writers using the term seem
to agree that the design of a data mart tends to start from an analysis of
user needs and that a data warehouse tends to start from an analysis of what
data already exists and how it can be collected in such a way that the data
can later be used. A data warehouse is a central aggregation of data (which
can be distributed physically); a data mart is a data repository that may
derive from a data warehouse or not and that emphasizes ease of access and
usability for a particular designed purpose. In general, a data warehouse
tends to be a strategic but somewhat unfinished concept; a data mart tends
to be tactical and aimed at meeting an immediate need.
One writer, Marc Demerest, suggests combining the ideas into a Universal Data
Architecture (UDA). In practice, many products and companies offering data
warehouse services also tend to offer data mart capabilities or services.
There can be multiple data marts inside a single corporation; each one relevant
to one or more business units for which it was designed. DMs may or may not
be dependent or related to other data marts in a single corporation. If the
data marts are designed using conformed facts and dimensions, then they will
be related. In some deployments, each department or business unit is considered
the owner of its data mart including all the hardware, software and data.[1]
This enables each department to use, manipulate and develop their data any
way they see fit; without altering information inside other data marts or
the data warehouse. In other deployments where conformed dimensions are used,
this business unit ownership will not hold true for shared dimensions like
customer, product, etc.