Building the Data Warehouse

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While such a possibility is certainly an option, however, it is almost never a good choice. Managing common current detailed data is difficult enough. The volumes of data found at that level present their own unique problems for management. Adding the complication of having to cross multiple technological platforms merely makes life more difficult. Unless there are very unusual mitigating circumstances, this option is not recommended.


The only advantage of multiple platforms for the management of common detail is that this option satisfies immediate political and organizational differences of opinion.


common data across many development groups

platform A    platform B    platform C


Figure 6.42 Common detailed data across multiple platforms-a real red flag in all cases.

Summary


Most environments operate from a single centralized data warehouse. But in some circumstances there can be a distributed data warehouse. The three types of distributed data warehouses are as follows:


■■ Data warehouses serving global businesses where there are local operations and a central operation


■■ Technologically distributed data warehouses where the volume of data is such that the data is spread over multiple physical volumes


■■ Disparate data warehouses that have grown separately through lack of organizational or political alignment


Each type of distributed data warehouses has its own considerations.


The most difficult aspect of a global data warehouse is the mapping done at the local level. The mapping must account for conversion, integration, and different business practices. The mapping is done iteratively. In many cases, the global data warehouse will be quite simple because only the corporate data that participates in business integration will be found in the global data warehouse. Much of the local data will never be passed to or participate in the loading of the global data warehouse. Access of global data is done according to the business needs of the analyst. As long as the analyst is focusing on a local business practice, access to global data is an acceptable practice.

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