Building the Data Warehouse

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Following are a few considerations of the elements of the indirect use of data warehouse data:


■■ The analysis program:


■■ Has many characteristics of artificial intelligence


■■ Has free rein to run on any data warehouse data that is available


■■ Is run in the background, where processing time is not an issue (or at least not a large issue)


■ Is run in harmony with the rate at which data warehouse changes


online


environment




analysis/ — preparation program


Figure 3.50 The way that data warehouse data is made available to the online operational environment—indirectly.

■■ The periodic refreshment:


■■ Occurs infrequently ■■ Operates in a replacement mode


■■ Moves the data from the technology supporting the data warehouse to the technology supporting the operational environment


■ The online preanalyzed data file:


■    Contains only a small amount of data per unit of data


■    May contain collectively a large amount of data (because there may be many units of data)


■    Contains precisely what the online clerk needs


■    Is not updated, but is periodically refreshed on a wholesale basis


■    Is part of the online high-performance environment ■■ Is efficient to access


■    Is geared for access of individual units of data, not massive sweeps of data

Star Joins


Data warehouse design is decidedly a world in which a normalized approach is the proper one. There are several very good reasons why normalization produces the optimal design for a data warehouse:

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