The defaultSessionCookieID build descriptor option identifies the session cookie provided to the EGL Rich UI Proxy from a service. The service logic in this case is stateful, which means that the user and logic can participate in a multistep conversation. This setting is meaningful only if the service is an EGL external type that makes an IBM® i called program or service program available as an EGL REST service. For background information, see Accessing IBM i programs as Web services.
The default value is JSESSIONID, which is always the session ID, regardless of any setting in EGL, when your application runs on Apache Tomcat.
For details on that choice, see Declaring an interface to access a REST service.