Hi I am doing deployment from sandbox to production using change sets. I adding some existing reports and dashboards to production. In this process any existing records loss in production?
Rajesh, no records will be lost due to deployment if you mean actual data but nothing will be transferred by Change Sets.
Using Change Sets an important factor to remember is check the permissions on objects, reports, report folders, page layout assignments, etc as Change Sets are not particularly good at transferring permissions in the deployment process.