Oracle BI Mind Confusing Questions

Question

Hi,
I am new to Oracle BI. I have been reading documents, tutorials, oracle by example guides and watching some videos.
But I cannot answer some questions which are confusing my mind.
1-) Why we have 3 repository layer? In the tutorials, they are dragging objects from physical layer to business model and mapping layer. In this layer they are renaming table names. Then they are dragging objects from Business Model to Presentation Layer. In this layer they are renaming table names again and they are deleting some columns. I think that we can use just physical layer and presentation layer. In presentation layer we can rename table names and remove some columns.
2-) In physical layer, we are importing objects from data sources. We can import tables, views and foreign keys. What is the best practice for designing business model?
I created a test repository. I imported tables, views and foreign keys from database. But when I try to check consistency ( afte preparing presentation layer), I took error messages about self joins in the physical layer. Can I solve self join problem?
3-) Should I import only tables and views from database in physical layer? I think that if I do not ceate joins manually after import operations, Oracle BI Server may not prepare correct sql statements.
We have a big database (maybe 500 tables), so if I dont import foreign keys, manually creating foreign keys will be a massive manual process. I also do not know which foreign keys are mandatory for a well designed business model?
4-) When database tables changed( for. ex. added new column), are these changes automatically updated to the physical layer?
Thank you..
Edited by: user4030266 on Mar 24, 2011 1:58 PM

Answer 1

3-) Should I import only tables and views from database in physical layer? Yes you need to import tables, you can create views on those tables if you want in physcial layer.
I think that if I do not ceate joins manually after import operations, Oracle BI Server may not prepare correct sql >statements.Yes you need to give proper joins between fact and dimension tables in physical and bmm layers.
We have a big database (maybe 500 tables), so if I dont import foreign keys, manually creating foreign keys will be a massive manual process. I also do not know which foreign keys are >mandatory for a well designed business model?Need to do datamodeling(ETL process first).Convert OLTP to OLAP(into facts and dimesnions) so that you will come to know regarding table and join conditions.
In BMM layer we write logics,create our own logical tables with logical columns,hierrarchies.We use only columns that we need in this layer and write logics upon them.
Refer : http://www.oraclebidwh.com/2010/10/obiee-bmm-layer-design-principalsbest-practices/
Regards,
Srikanth