Call now: 252-767-6166  
Oracle Training Oracle Support Development Oracle Apps

 E-mail Us
 Oracle Articles
New Oracle Articles

 Oracle Training
 Oracle Tips

 Oracle Forum
 Class Catalog

 Remote DBA
 Oracle Tuning
 Emergency 911
 RAC Support
 Apps Support
 Oracle Support

 SQL Tuning

 Oracle UNIX
 Oracle Linux
 Remote s
 Remote plans
 Application Server

 Oracle Forms
 Oracle Portal
 App Upgrades
 SQL Server
 Oracle Concepts
 Software Support

 Remote S


 Consulting Staff
 Consulting Prices
 Help Wanted!


 Oracle Posters
 Oracle Books

 Oracle Scripts

Don Burleson Blog 







Relational OLAP

Oracle Tips by Burleson Consulting

The Data Warehouse Development Life Cycle

Online Analytical Processing and Oracle

Relational OLAP (ROLAP)

Because the entire enterprise can be made available to a ROLAP tool, it is not surprising to acknowledge that ROLAP is far more flexible than its MOLAP cousin. Any data, on any platform or database, can be mapped into a multidimensional format; the ROLAP engine will obediently extract and summarize the data according to the extraction specifications. Because ROLAP is far more robust in this sense, it is the OLAP tool of choice for data warehouses that support the following features:

*Data changes frequently--In a data warehouse where data is very dynamic and end users require up-to-the-minute summarizations, ROLAP is the only choice. MOLAP tools must extract and summarize data offline for loading into their multidimensional databases. To make matters worse, most multidimensional databases require recalculation of the entire database when a new dimension is added, an aggregation scheme changes, or data is added. These overhead factors make MOLAP inappropriate for decision support systems with highly volatile data sources. Examples of these types of applications include stock market DSS and weather forecasting tools.

*Large data volumes--For very large database warehouses in the terabyte range, the cost of supporting MOLAP tools can be exorbitant. The pre-summarization of data can require hundreds of gigabytes of disk storage, and many companies cannot afford the millions of extra dollars required to provide sub-second response times for OLAP queries. ROLAP tools allow companies to leverage their existing investment in OLTP databases without having to buy a multidimensional engine.

*Unpredictable types of queries--Because ROLAP engines can allow virtually any operational data source to be queried and summarized, ROLAP has a clear advantage for the decision support application that cannot predefine its query requirements. Of course, this flexibility comes at the cost of ease-of-use, because the IS department must often get involved to assist end users in creating the mappings to the operational databases.

Today, many developers are using relational databases to build their data warehouses and simulate multiple dimensions, and specific design techniques are being used for this. The push toward STAR schema design has been somewhat successful, especially because designers do not have to buy multidimensional databases or invest in expensive front end tools.

Several methods can be used to aggregate data within OLAP servers. As you can see in Figure 5.18, this method extracts data from the relational engine and summarizes the data for display. Another popular method pre-aggregates the data and keeps the summarized data ready for retrieval.

Figure 5.18  Aggregation and OLAP servers.

This is an excerpt from "High Performance Data Warehousing", copyright 1997.
If you like Oracle tuning, you may enjoy the book Oracle Tuning: The Definitive Reference , with over 900 pages of BC's favorite tuning tips & scripts. 

You can buy it directly from the publisher and save 30%, and get instant access to the code depot of Oracle tuning scripts.
Oracle Training at Sea
oracle dba poster

Follow us on Twitter 
Oracle performance tuning software 
Oracle Linux poster


Burleson is the American Team

Note: This Oracle documentation was created as a support and Oracle training reference for use by our DBA performance tuning consulting professionals.  Feel free to ask questions on our Oracle forum.

Verify experience! Anyone considering using the services of an Oracle support expert should independently investigate their credentials and experience, and not rely on advertisements and self-proclaimed expertise. All legitimate Oracle experts publish their Oracle qualifications.

Errata?  Oracle technology is changing and we strive to update our BC Oracle support information.  If you find an error or have a suggestion for improving our content, we would appreciate your feedback.  Just  e-mail:  

and include the URL for the page.


Burleson Consulting

The Oracle of Database Support

Oracle Performance Tuning

Remote DBA Services


Copyright © 1996 -  2020

All rights reserved by Burleson

Oracle ® is the registered trademark of Oracle Corporation.