All this talk of "browsing" result sets and sending back sections of them
suggests an application server is the right answer.

Let the web application establish a session with the app server which
corresponds with the web user's session. The app server does the query to
the database server and can then send sections of the result set to the web
app, as requested. If the web app goes away the app server times out the
session and closes the query releasing all cached results. This does not
cause the database server to do more than is reasonable for a database server.