Building the Data Warehouse

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many as 10,000 terminals in a single DSS network, trying to administer the monitoring of each terminal is nearly impossible.

The alternative is to do the monitoring of the DSS system at the server level. After the query has been formulated and passed to the server that manages the data warehouse, the monitoring of activity can occur. Undoubtedly, administration of the monitor is much easier here. But there is a very good possibility that a systemwide performance penalty will be incurred. Because the monitor is using resources at the server, the impact on performance is felt throughout the DSS data warehouse environment. The placement of the monitor is an important issue that must be thought out carefully. The trade-off is between ease of administration and minimization of performance requirements.

One of the most powerful uses of a monitor is to be able to compare today’s results against an “average” day. When unusual system conditions occur, it is often useful to ask, “How different is today from the average day?” In many cases, it will be seen that the variations in performance are not nearly as bad as imagined. But in order to make such a comparison, there needs to be an average-day profile, which contains the standard important measures that describe a day in the DSS environment. Once the current day is measured, it can then be compared to the average-day profile.

Of course, the average day changes over time, and it makes sense to track these changes periodically so that long-term system trends can be measured.

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