Hi Enrique . . .
Yes. Today the ECC system is running on a traditional RDBMS. But it will soon migrate to HANA. This migration will allow some operational reporting use cases to move off of the current HANA based EDW back into the SoH system.
Similarly, the use of virtual tables (in the OLAP HANA) via SDA connectivity into the physical table on the SOH is viable for some other use cases.
But where there is heavy duty modeling across many tables (some Non-SAP) and the reporting granularity involves large result sets - this will put heavy load on the OLTP system to feed data into OLAP HANA over SDA connections. This is why the customer is contemplating keeping physical replicas in the EDW: because there are certain use cases that just don't belong in the OLTP HANA. And are best serviced by materialized objects in the EDW HANA.
regards,
Keith