Sandeep,
I'm not pretty sure, but I heard a third party tool like Star Analytics (which is recently been acquired by IBM and named as CIS).Or there is no direct way.
It is better to rebuild the report from the scratch. Qlikview interact with data directly whereas Cognos reports are more static with at most prompts. And, qlikview has a AQL technology for which we need to make sure our data model is designed properly. Once you data model is ready, you will be in position to query your entire data on a Qlik of a button. Since its a Inmemory technology, you have sure it follow qlikview best practices to avoid excess consumption of RAM.
Regards.
Siva
