DW Basics: What is a Data Mart ?

A Data Mart is a part of the Data Warehouse or a set of dimensions and fact tables that is concentrated on a particular area of a business.

Consider the example of an IT organization, the organization will be having many sub domains like HR, Finance, Sales, Recruitment etc.In a Data warehouse the data from all the subdomains will be available. A data mart is simply all the dimension or fact tables that are based on a single subject area, for example all the dimension and fact tables related to the Finance department would come under Finances data mart. 

Definition for a Data Mart is as follows,

Oracle - A data mart is a simple form of a data warehouse that is focused on a single subject (or functional area), such as Sales, Finance, or Marketing. Data marts are often built and controlled by a single department within an organization. 

Wikipedia - The data mart is a subset of the data warehouse that is usually oriented to a specific business line or team. Data marts are small slices of the data warehouse.