This is the length of time the current connection between the SmartEvent server and a specific Correlation Unit has been continuously up. A duration that keeps resetting to a small number rather than climbing steadily indicates the connection to that Correlation Unit is repeatedly dropping and reconnecting, a leading indicator of an unstable link worth fixing before it causes an actual event-processing gap. For example, this value resetting to under a minute every few minutes would reveal a flapping connection to that Correlation Unit long before the last-received-event timestamp shows an outright gap.