Q: I have read about concept of hot,cold data in HANA, table loading and unloading etc.Is that applicable only for BW on HANA?
No, that is also possible for non BW data. One example is the use of so called data aging objects, enabeling you to offload e.g. data of older fiscal years from the HANA memory, see also: Data Aging - SAP Library
Q:What happens incase of ECC on HANA? Can we unload tables from memory and store on disk so that HANA will load it to memory when any read/write request comes through? please clarify.
A: -> see answer aqbove. Beside that ythere are also other ways to influence what SAP tables needs to be kept in memory or on disk (that more a HANA question, ask that to the HANA SDN space)
Regards, Nico Kuijper