Building the Data Warehouse

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ISSUE: One of the primary features of the data warehouse is ease of accessibility of data. And the first step in the accessibility of data is the initial location of the data.

46.    Will there be an attempt to mix operational and DSS processing on the same machine at the same time? (Why? How much processing? How much data?)

ISSUE: For a multitude of reasons, it makes little sense to mix operational and DSS processing on the same machine at the same time. Only where there are small amounts of data and small amounts of processing should there be a mixture. But these are not the conditions under which the data warehouse environment is most cost-effective. (See my previous book Data Architecture: The Information Paradigm [QED/Wiley, 1992] for an in-depth discussion of this issue.)

47.    How much data will flow back to the operational level from the data warehouse level? At what rate? At what volume? Under what response time constraints? Will the flowback be summarized data or individual units of data?

ISSUE: As a rule, data flows from the operational to the warehouse level to the departmental to the individual levels of processing. There are some notable exceptions. As long as not too much data “backflows,” and as long as the backflow is done in a disciplined fashion, there usually is no problem. If there is a lot of data engaged in backflow, then a red flag should be raised.

48.    How much repetitive processing will occur against the data warehouse environment? Will precalculation and storage of derived data save processing time?

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