If you call SAP application through browser and get the error "Dispatcher running but no server connected" and jcmon tool shows server nodes in Running status, check the following:
- Ensure that the joinPort (5NN20) is not used by any other process in the OS
- Ensure that the server node is not set in debug mode. The dispatcher will not route the requests to the server node that is running on debug mode.
- Check the parameter elements in the service r3setup. Ensure that the value is not 0. It should be equal to the number of server nodes clustered with the dispatcher
- Check if there are repeated full GCs running on the server node