Key Fields for DSO using 2lis_02_SCL and 2lis_02_ITM

Hi All

I'm doing the data model design for procurement and i'm intending to use standard cube 0PUR_C01, but instead of using the standard flow (directly from DS to Cube) i was wondering to load the data firstly to one DSO (with all the detail) and next to the cube.

Lost while creating the DSO's . What are the keys we need in DSO when we are loading 2lis_02_SCL and 2lis_02_ITM .

Kindly share your experience ,

Thanks in advance!!!