When trying to access, browser is returning below error: Error: Service Unavailable HTTP Error 503. The service is unavailable. Reason: This error occurs usually when default pool stopped. Solution: Go to Siebel web server, from the start open Internet Information Services (IIS) Manager and click on "Application Pools" From the Application Pools, right click on "DefaultAppPool" and from menu click on "Start". Wait for some time and re try to access the Siebel app url.