Building the Data Warehouse

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In the same vein, the data must be monitored at will. The cost of monitoring data cannot be so high and the complexity of monitoring data so great as to inhibit a monitoring program from being run whenever necessary. Unlike the monitoring of transaction processing, where the transactions themselves are monitored, data warehouse activity monitoring determines what data has and has not been used.

Monitoring data warehouse data determines such factors as the following:

■■ If a reorganization needs to be done

■■ If an index is poorly structured

■■ If too much or not enough data is in overflow

■■ The statistical composition of the access of the data

■ Available remaining space

If the technology that houses the data warehouse does not support easy and efficient monitoring of data in the warehouse, it is not appropriate.

Interfaces to Many Technologies

Another extremely important component of the data warehouse is the ability both to receive data from and to pass data to a wide variety of technologies. Data passes into the data warehouse from the operational environment and the ODS, and from the data warehouse into data marts, DSS applications, exploration and data mining warehouses, and alternate storage. This passage must be smooth and easy. The technology supporting the data warehouse is practically worthless if there are major constraints for data passing to and from the data warehouse.

In addition to being efficient and easy to use, the interface to and from the data warehouse must be able to operate in a batch mode. Operating in an online mode is interesting but not terribly useful. Usually a period of dormancy exists from the moment that the data arrives in the operational environment until the data is ready to be passed to the data warehouse. Because of this latency, online passage of data into the data warehouse is almost nonexistent (as opposed to online movement of data into a class I ODS).

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