An evaluation of Oracle BI Enterprise Edition from Intelligent Enterprise

A good article from Intelligent Enterprise about the Oracle BI Enterprise Edition - Put to the test: Oracle BI Enterprise Edition.

Here is the part I feel worth highlight:

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Aggregation for Data Warehouse, Part 2

In the aggregation for Data Warehouse, Part 1, I mentioned that there are multiple ways to do the aggregation for data warehouse. One of the method is to use the ETL tool to maintain the aggregated tables.

Aggregation for Data Warehouse, Part I

A data warehouse typically contains historical data that are viewed in a summary form and then let the users to drill down to the more detail transactions. The fact data can easily reach the size of gigabytes to terabytes. Summarizing the huge volume of the fact data online may not be practical.

One of the techniques employed by data warehouse designers to improve performance is the creation of summaries, or aggregated tables, which contains pre-calculated data.

For example, you may see the costs against your project with a inception to date amount, which include the historical cost charged against the project up to the current date. Without the pre-calculated data, a query to fetch the ITD amount may take minutes to fetch and summarize the fact data. Using an aggregated table, the amount is periodically refreshed with the amounts from the recent transactions in the latest summarization process. Fetching the data online from the aggregated table probably takes only seconds.

There are multiple ways to create such aggregations: