The connection pool will close and discard active connections that have been busy or idle for a long time, the default being 2 minutes. This helps in server recovery from stuck SQL, connection leaks and deadlocks not detected by the database server. If you have queries that take more than 2 minutes to execute or obtain DB connections from the IObjectScope and keep them idle you may need to disable this feature by setting the timeout to 0 (see Active con timeout).
A driver.pool.contimeout event is logged when connections are timed out, if the event logging level is set to anything other than "none". This should be considered a serious error.