DSO's for 0CO_PC_01 / 0CO_PC_02 and Validate against ECC?

Hi Guys,

I have activated COst Object controlling : 0CO_PC_01 / 0CO_PC_02 and standard content cube 0PC_C01 for this. I want to do following:

1) Put datawarehousing DSO (standard) layer before going to Cube. (i.e Datasources will load to DSO and each of DSo will load to Cube)

2) Convert 3.X infosources to 7.0 Transformations.

I have converted 3.X Transfer routines etc to transformations and build DSO layer for each of extractors:.

I have following questions:

1) What key fields should be considered for DSO?

2) How to validate data in BI cube back to ECC? Any standard report / transaction / table would help.

3) Any issues you have faced with these extractors?

Thanks

SA