Guide to Data Warehousing and Business Intelligence
A Data Mart is a subset of data from a Data Warehouse. Data Marts are built for specific user groups. They contain a subset of rows and columns that are of interest to the particular audience. By providing decision makers with only a subset of the data from the Data Warehouse, privacy, performance and clarity objectives can be attained.
There are different types of Data Marts. A Data Mart can be a physically separate data store from the Corporate Data Warehouse or it can be a logical "view" of rows and columns from the Warehouse.
Data Marts can be architected to support online queries and data mining (i.e. dimensional design) or then can be designed to support more conventional reporting needs (i.e. relational design).
In some organizations, a Data Warehouse might not physically exist. Logically, however, it exists as the sum of all the "conformed" Data Marts.