Thursday, March 21, 2013

Data Warehouse Architecture (with a Staging Area and Data Marts)

Although the architecture in Figure 1-3 is quite common, you may want to customize your warehouse's architecture for different groups within your organization. You can do this by adding data marts, which are systems designed for a particular line of business. Figure 1-4 illustrates an example where purchasing, sales, and inventories are separated. In this example, a financial analyst might want to analyze historical data for purchases and sales.

Data mart
Similar to a data warehouse, but holding only the data needed for a specific business function or department . Different data marts may be stored in different locations on different platforms using different database products.

Mart or warehouse?
A data mart need not be small, but is likely to contain a subset or summary of the detailed information available in the warehouse. It will be structured to optimize the specific reports and analyses needed by a clearly defined group of users, and is much easier to build than a complete data warehouse. 
A central data warehouse can feed multiple data marts, with overlapping content. Each mart then provides a customized view of the organization, based on consistent data from the main warehouse.
The warehouse may be allowed to grow from the first mart to be implemented, possibly sharing the same hardware platform and database. This approach can lead to major problems and rework as the warehouse expands .

Data staging
The process of extracting, transforming, loading and checking data on its way from source system to data warehouse. Copies may be stored at intermediate steps in a data staging area.
The most difficult and time-consuming aspect of building a data warehouse is taking data from disparate source systems, converting them into a consistent form that can be loaded into the warehouse, checking their quality and automating this process. 

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