The Web environment is not based on persistent connections between the browser and the http server. When you run the WebFaced application and leave the browser for an extended period of time, the application will actually time out (see Figure 18.10).
In this environment, the server cannot detect whether a session has been interrupted permanently by problems with communications or by the workstation itself. To avoid having too many invalid sessions, the application server has a default session time out of 30 minutes. By default, a session will be invalidated after 30 minutes of idle time. If you try to use the session after 30 minutes of inactivity, you will see this error.
If this time interval of 30 minutes does not suit your environment, you can change the application server settings using the Administration console to change the time out values.