As described in
Defining state, Web requests can be sent in a stateless mode or in a state-aware mode. In the stateless mode, web requests are independent of each other. No application context is maintained from one request to another. In state-aware mode, context is maintained by locking a WebSpeed agent to a particular client. State-aware mode has a scalability disadvantage because the locked agent is not available until a session is completed.
When you enable Session Connection ID, the WebSpeed Messenger checks incoming requests for a cookie containing a value for SERVER-CONNECTION-ID. The SERVER-CONNECTION-ID variable contains a unique identifier. If it does not exist, the WebSpeed Messenger causes a unique identifier to be generated. The WebSpeed Messenger then sets the SERVER-CONNECTION-ID attribute of the SESSION handle to the value of the unique identifier. (For more information, see OpenEdge Development: ABL Reference.) This unique connection identifier gets passed to the WebSpeed Agent as part of the Web request. In turn, the WebSpeed Agent passes the unique connection identifier to the WebSpeed application (also known as the Web object).