OBIEE Interview Question- Dimensional Hierarchy

What is dimensional hierarchy? How you define number of elements at each level? Can it be done automatically?

A dimensional hierarchy is created in the BMM layer of a repository to calculate level based measures and to create interactive reports/dashboards with drill down functionality.

A dimension hierarchy can be created manually as well as automatically. Manual process involves right clicking on BMM layer> New Object> Dimension, entering a name; right clickking on this new dimension and create New Level.

Levels are base on the business definition or hierarchy of a dimension, a classic example; year> quarter> Month> week> Day. A hierarchy will have at least two levels, Grand Total Level and Detail Level. For each level we have to define the number of elements. This is always 1 for the Grand Total Level and next levels are the ratio from one level on top to the bottom.

When creating a dimension automatically, we have to right click on the dimension and click Create Dimension. This will automatically create the two levels Grand Total and Detail Level.

We can actually automatically calculate number of elements at each level. The procedure is to open a repository in online mode. Right click on business model or dimension hierarchy and click on estimate levels.


Cheers!
Deepak

How to get started with OBIEE

I always come across people who are interested in learning OBIEE, and they become curious to know about BI. They always ask me how to learn OBIEE.

My first answer is to get familiar with Data Warehousing concepts. A good understanding of the following is needed to succeed as an OBIEE Developer:

- Database/ Data Warehouse/ Data Mart

- SQL

- Data Modeling

- OLTP & OLAP Systems

-  Star & Snowflake Schema

- Facts & Dimensions

- Slowly Changing Dimension

- Other DW concepts- Hierarchy, Confirmed Dimension, Bridge Table, Implicit Fact, Fact less Fact, Aggregate table and more

A lot can be learned from Wikipedia as well, some of the topics about BI and Data Warehousing are very well explained.

Read The Data Warehouse Toolkit: The Complete Guide to Dimensional Modeling to build an understanding of dimensional modeling.

Once you are through with all of the above start working on Oracle by Examples http://apex.oracle.com/pls/apex/f?p=9830:bi:1287755467524366::NO:::

Join OTN to gain from other’s experiences. Please follow Forum Etiquettes. I would suggest start reading the questions which have been answered in the forums.

And of course, there are so many blogs on OBIEE that can help you develop your OBIEE skills. So, join me in the journey of OBIEE.

Cheers!

Deepak