Hello Rahul,
Please check following SAP document where exact steps to replicate Source system mapping have been mentioned without effecting data models in the events of system refresh.
Faqs can be found in the following note:-
For pointers on the issue
1059278 - 70SP15: Error in transaction BDLS
886102 - System Landscape Copy for SAP NetWeaver BW
I hope this helps you in complete understanding and resolution of issue.
Regards
Anand