Hi Swathi
Option 1) Hana as Secondary Data base- SAP ECC is still on say DB6 (HANA is OLAP and ECC is OLTP ) ------>
HANA is neither OLTP nor OLAP. You can use the HANA database for storing data(-read tables) OLAP or OLTP does not matter.
Option 2)Is there a way to migrate your SAP ECC DB6 (or any ECC Database) to HANA Database and use SAP ECC as both your OLAP and OLTP Systems ------->
If you are thinking along the lines of the ECC database residing on HANA, technically that is possible. Considering that the ECC system is generally a system of record it has to be extremely reliable , robust with recovery/audit features among other things. Some time in the future that might happen. And you are right, in that scenario there is would be no need for SLT, BODS, DXC or anything else.
Option3)Say we already have BW system in Place what happens in that case
1)SAP ECC(DATA)--->BW(Cubes)--> HANA(Migrate your existing cubes to Views(Analytic or calculation Views) if this right- when we want to create a new View -Do we have to create Cube in BW and Migrate to View in Hana Studio) -------->
I agree with Ravindra's response to this part of your question.
Regards
Srinivas Rao