Hi Rohit
I hope you are taking back-up of planning area in cube. You can copy the data from cube to planning area. For your further understanding go through SAP notes (though version wise they are old but will give an understanding):
385808 - APO liveCache Backup Strategy: Recommendations
391625 - Backup and Recovery for APO 3.0A Demand Planning
and check point number 10 in below SAP note
500843 - Composite SAP note for COM and SAP liveCache 7.2 or higher
If this answers your question follow How to close a discussion and why else raise your concern.
Regards
Rahul