If you are using an SAP HANA database for your BW system, the virtual data mart layer replaces the virtualization layer. The virtual data mart layer contains all InfoProviders that
combine data using join or union, without saving the result: MultiProvider, CompositeProvider
access data directly in the SAP HANA database, to allow queries on the data: TransientProviders based on the SAP HANA model and VirtualProviders based on the SAP HANA model
The layer creates parenthesis, which include all persistency layers but which also remain flexible.