Hi,
Consider 4 cubes CR1, CR2, CR3, CR4 under one multiprovider where CR1 has region1 data, CR2 has region 2 data etc. Once the query is executed by region1 user then he should see data from CR1 cube- Am i right?.
I believe some info object like 0SOURCESYSTEM must be there inroder to distinguish what region does the cube data belongs.
If yes, then just restrict the query info provider such a way that it's determined by a customer exit variable based on roles assigned to user whoever executing determine the region from it then determine the cube that belongs to that region( concatenate CR and region to determine cube). Maintain 0TCAIPROV as ZCR* .
We are working on similar landscape as you said and we do have a z info object and restricted query with that info object which is determined by customer exit based on roles for end user or based on user maintainence in a dso ( z info object customer exit determines the region for e.g. 600 which has R3 source system with client 600).
Hope it helps.
Srikanth.