Dear Pavan,
Can you confirm once again that, where you are creating datasource - is it in BI system or ECC side.
If you are using Transaction RSA1 at BI side it means that you are creating datasource through Flat File.
First check Flat file source connection , under source system tab at RSA1.
By reading your thread , I guess that you are triggering transaction RSA1 in ECC side. Confirm on this.
If you want to create Datasource in ECC side use T code - RSO2 and use method Table/View/FM/Infoset query.
Regards,
Vijay