Uniqueness of level

[bloggerman]

I have heard that we should have the lowest level in the dimension set to unique

1)    My question is what would happen if i dont set it to unique
2)    And, why set only the lowest level as unique

[tjohnson3050]

http://www-01.ibm.com/support/docview.wss?uid=swg21496948&aid=1

[bloggerman]

This seemed for FM. Is it relevant to Transformer too?

[tjohnson3050]

http://www.biprofessional.com/2011/02/cognos-transformer-and-category-uniqueness-part-1/