Hello Tuhin,Using server side session is not recommended in AEM, you can not cache pages and use proper load balancing if server side session is enabled. Would recommend to save this data to either client context or cookie or query param or Use some kind of session storage (couch base or something)....

Namespace should be stored under crx-quickstart/repository/repository in file system (Restart may require). You can also remove namespace using API http://www.day.com/specs/jcr/1.0/7.2_Adding_and_Deleting_Namespaces.htmlYogesh