Hi Jagaa,
1 . The compression technique used in sap hana ? Can any briefly explain this ....
In addition to what Patrick mentioned, I would advise you tot take the free open Course at OpenHPI to get better understanding of how HANA works and to know more about Compression techniques like Dictionary Encoding, Run Length Coding:
Course: In-Memory Data Management
2. If hana stores everything in ram...suppose the ram is full of data ...now we want insert the data in to hana ...then hana still allows it store ?
Regarding HANA Memory Usage, I would suggest you to go through this Whitepaper and all your queries will be solved
SAP HANA Memory Usage Explained | SAP HANA
3. In hana , all the data is in ram ,,, but we only use the limited data in ram .... Suppose we hava data which is not at all used ....then still data is ram or somewhere?
Already answered by Patrick above
Additionally check the below blog for links to HANA Architecture reference materials:
HANA Reference for Developers - Links and SAP Notes(Part-1) - Updated 04.12.2013
Regards,
Vivek