Data Warehouses and Multidimensional Databases Oracle Tips by Burleson Consulting

High Performance Data Warehousing

Data Warehouses And Multidimensional Databases  

* Pre-joining tables together--This is an obtuse way of saying that a denormalized table is created from a normalized online database. A large pre-join of several tables is sometimes called a fact table in a STAR schema.

* Pre-summarization--This prepares the data for any drill-down requests that may come from an end user. Essentially, the different levels of aggregation are identified, and aggregate tables are computed and populated when the data is loaded.

* Massive denormalization--The side effect of very inexpensive disks has been the rethinking of the merits of third normal form. Today, redundancy is widely accepted, as seen by the popularity of replication tools, snapshot utilities, and non-first-normal-form databases. If you can pre-create every possible result table at load time, your end user will enjoy excellent response time when making queries. The STAR schema is an example of massive de-normalization.

* Controlled periodic batch updating--New detail data is rolled into the aggregate table on a periodic basis while the online system is down, with all summarization recalculated as the new data is introduced into the database. While data loading is important, it is only one component of the tools for loading a warehouse. There are several categories of tools that can be used to populate warehouses, including: