Generally Data mart is a subset of data warehouse system and it supports a specific business unit or business function.
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.
Data warehouses and data marts are built on dimensional data modeling where fact tables are connected with dimension tables. In a dependent data mart, data can be derived from an enterprise-wide data warehouse. In an independent data mart, data can be collected directly from sources.
Reasons for creating a data mart:
- Easy access to frequently needed data.
- Creates collective view by a group of users.
- Improves end-user response time.
- Ease of creation.
- Lower cost than implementing a full Data warehouse.
- Potential users are more clearly defined than in a full Data warehouse.