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Snowflake vs star schema in obiee 12c RPD
Dear All,
Snowflake vs star schema in obiee 12c RPD
Current scenario
Snowflake with 5 tables
Region category and country fetched through 3 tables snowflaked with the dimension customer.
through ETL we can load the country region and category information to the customer table and make it a star schema.
Can somebody help me to understand the advantages and disadvantages in terms of performance and other aspects. It would be a great help
Answers
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You can leave the snowflake at the physical layer and model the logical layer as a star (which obiee requires to function). So you can have the logical dimension with 4 tables as logical table sources then join that logical dimension to your fact. You'd see the snowflaking in the physical SQL sent back to the DB, but providing tuning and architecture there it shouldn't be an issue. So the answer to the either/or question is BOTH!
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To expand on 'how' in the business model layer you would expand the LTS source folder and drag the outer limb of the star onto the already modelled inner dimension. This will combine the two tables via a join showing one LTS and you can then change the nature of the join if you wish.
This means your snowflake is flattened into a star in the logical layer.
Does it perform as well as Fact -> Dimension - well no, to combine both into a single physical table would be better, but as the learned gentleman says with adequate tuning and architecture it will not be bad.
Best star
Second best snowflake
Worst 3NF
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