The SessionID and SessionCreateTime connection properties are useful for determining whether the current connection is within a session context. If either connection property query returns an empty string, then the session does not exist. The SessionCreateTime property provides a metric of when a given session was created. It is defined immediately at the time that the sa_set_http_option call is made. The SessionLastTime property provides the time that the session was last used. More specifically, it is the time when the last processed request for the session released the database connection upon termination of that previous request. The SessionLastTime connection property is returned as an empty string when the session is first created until the request (that created the session) releases the connection.