It is a subset of data warehouse and it supports a particular region, business unit like Sales, Marketing, HR, Finance. DW’s and DM’s are built on dimensional data modeling where fact tables are connected with dimension tables.
In an independent data mart, data can be collected directly from sources
In an dependent data mart, data can be derived from an enterprise data warehouse.
A data mart can contain operational data, summarized data, spatial data, or meta-data.
Data mart is a limited set of dimensions and measures used for specific business theme. They are populated out of the Data-Warehouse Data Sets.
Typically an organization’s business intelligence agenda starts with few data marts, before maturing to a full-blown data warehouse. However, most of the design & development concept apply equally to a Data-mart.