Comparative study of Data Warehouse and Data Mart

Before we are going to compare data warehouse and data mart first we have to define what “data mart” is.
In simple words we can define data mart as “specialized, subject-oriented, integrated, volatile, time-variant data store in support of a specific subset of management’s decisions”. It is actually a specialized version of a data warehouse, where it contains a snapshot of operational data, predicated on a specific, predefined need for a certain grouping and configuration of select data.
There can be multiple data marts inside a single corporation; each one relevant to one or more business units for which it was designed. Data Marts 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 their data mart which includes all the “hardware, software and data.” 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.
So, we found that data marts are actually some sub-set of a Data Warehouse, where they are maintained for the ease of the business people. There is no way that, when a data mart reaches certain size, it becomes data warehouse, or some collections of data marts comprise or become a substitute for a data warehouse. No matter how many characteristics they have in common, data marts and data warehouses will always be different. They can not be used interchangeably, and it’s only when they’re paired together that they operate at their optimal potential.