REF - Star vs. Snowflake Schemas / Star Transformation with a Bitmap Index

REF - Star vs. Snowflake Schemas / Star Transformation with a Bitmap Index

"A star schema optimizes performance by keeping queries simple and providing 
fast response time. All the information about each level is stored in one row.

Oracle Corporation recommends that you choose a star schema unless you have a 
clear reason not to."

REFERENCE:
   Star Schemas

"Snowflake schemas normalize dimensions to eliminate redundancy. That is, the 
dimension data has been grouped into multiple tables instead of one large table. 

...

While this saves space, it increases the number of dimension tables and requires 
more foreign key joins. The result is more complex queries and reduced query 
performance."

REFERENCE:
   Schema Modeling Techniques

"To get the best possible performance for star queries, it is important to follow 
some basic guidelines:

   - A bitmap index should be built on each of the foreign key columns of the 
   fact table or tables. 

   - The initialization parameter STAR_TRANSFORMATION_ENABLED should be set to 
   true. This enables an important optimizer feature for star-queries. It is set 
   to false by default for backward-compatibility. 

   - The cost-based optimizer should be used. This does not apply solely to star 
   schemas: all data warehouses should always use the cost-based optimizer."

REFERENCE:
   Optimizing Star Queries

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REFERENCE:
   Star Schema question on AskTom