Data Marts in DWH

 A data mart is a single form of a data ware house that is focused on a single subject or functional area such as sales or finance or marking. It is often build and controlled by a single department within an organization.It draws data from only few sources. The source could be internal operational system, a central data warehouse or external data. Data marts are small in size and more flexible compared to data ware house.

In other word we can say that Data mart is a subset of Data ware house oriented to a specific business line.

Below is the type of Data Mart

Ø  Dependent : Dependent data marts are created by drawing data directly from operational, external or both sources

Ø  Independent: Independent data mart is created without the use of a central data warehouse.

Ø  Hybrid:  This type of data marts can take data from data warehouses or operational systems.

Dependent Data Mart

In a dependent data mart, data is sourced from the existing data warehouse itself. This is a top-down approach because the portion of restructured data into the data mart is extracted from the centralized data warehouse.

A data mart can use DW data either logically or physically as shown below:

Ø  Logical View: In this scenario, data mart’s data is not physically separated from the DW. It refers to DW data through virtual views (or) tables logically.

Ø  Physical subset: In this scenario, data mart’s data is physically separated from the DW.

Once one or more data marts are developed, we can allow the users to access only the data marts (or) to access both Data marts and Data warehouses. ETT is a simplified process in the case of dependent data marts because the usable data already exists in the centralized DW. The accurate set of summarized data should be just moved to the respective data marts.

Independent Data Mart

An independent data mart is best suitable for small departments in an organization. Here data is not sourced from the existing data warehouse. The Independent data mart is neither dependent on enterprise DW nor other data marts. Independent data marts are stand-alone systems where data is extracted, transformed and loaded from external (or) internal data sources. These are easy to design and maintain until it is supporting simple department wise business needs.

We have to work with each phase of the ETT process in case of independent data marts in a similar way as to how the data has been processed into centralized DW. However, the number of sources and the data populated to the data marts may be less.

Hybrid

In a hybrid data mart, data is integrated from both the DW and other operational systems. Hybrid data marts are flexible with large storage structures. It can also refer to other data marts data.