You can use this connection parameter in order to keep an idle connection for a prolonged period of time and be sure that it was not broken. Just specify a non-zero interval in seonds in this parameter, and the connection will perform periodic ping calls to PostgreSQL. If such call fails, the StateChange event occurs.
We recommend to use this parameter only when it is necessary to keep idle connection alive for long periods of time. We do not recommend using it when it's not needed.