Hi Rahul,
Regarding cache size details in BODS please refer below thread.
Links
http://scn.sap.com/thread/3258066
http://scn.sap.com/thread/2078942
http://scn.sap.com/thread/1543833
Or refer below Snotes
1747494 - Data Services and load balanced ECC and BW environment
https://service.sap.com/sap/support/notes/1747494
1760987 - Configuring sapnwrfc.ini to utilize a message server to connect to SAP (ECC, BW) Servers - Data Services 4.x
https://service.sap.com/sap/support/notes/1760987
Thanks,
Daya