Pratap,
in BW on traditional RDBMS, the data need to be moved from the database server to the applications server(s) in order to get activated. This creates a lot of network traffic and overhead in general and of course delay in the process while moving the data back and forth..
In BW on HANA the activation is processed on the SAP HANA database server directly.
More details you can find in here: Data Modeling - BW InfoProviders
thanks
erich