After restarting the JIRA, i was re-rerouted to the configuration page after few seconds the app is running. Before got rerouted, i was able to login to the JIRA and view issues that was created before the restart.
I have done the reconfiguration, but after i restart the JIRA (after performing the new config), i am again able to access to the JIRA with my login that i used before the restart and i was able to view the existing issues that was created before the first restart. After few seconds, when i want to view the issue, it got redirected to the login page which i can access it with my newly created account. But all the existing issue is gone. I have checked the DB, all issues created are still kept in the DB.