Non Unique Indexes on Dimension Table

Hello ,

I have Material Dimension that has Product MainGroup, Brand , SPC code broken from Product Hierarchy.

As per Business Requirement , we don't want to use the Product Hierarchy , that should need to split into 3 pieces.

Since The Cube Dimensions already reached the 13 , we can not increase the dimensions to keep these 3 fields into separate dimensions.

I heard from Basis guy as <b>we can have index on three fields in same dimension table</b> & read some negative impact on aggregate definition.

Is it true , which one is true , am not sure.

Which one impact causes more worst & usefull..?

Could please some experts throw some light on this.

Cheers

Martin