When this type of monitoring is configured, Directory Proxy Server listens for errors on the traffic between itself and the data source. If Directory Proxy Server detects that a client operation fails, the proxy tests the data source related to the failure.
This type of monitoring is called reactive monitoring because Directory Proxy Server reacts to an error, but otherwise performs no active testing of the data sources.
Directory Proxy Server can be configured to perform this type of reactive monitoring only, without performing the monitoring described in Monitoring Data Sources by Periodically Establishing Dedicated Connections and Monitoring Data Sources by Testing Established Connections. When only reactive monitoring is configured, the monitoring less complete but does not cause additional traffic.