Data source monitoring can flag the events so that they are treated as a problem and resolution event.
When Netcool/Impact fails to establish a connection to a data source, it sends a connection failure event to OMNIbus which is flagged as problem event. When a successful connection is established to the same data source, a connection established event is sent to OMNIbus. This connection is flagged as a resolution event. It sets the necessary information in the Node, AlertKey, AlertGroup, and Manager fields. Then the generic_clear trigger in OMNIbus identifies the problem and resolution event as a pair and eventually resolves the events.
In OMNIbus, the generic_clear trigger looks for resolution events where Type = 2 (Resolution event) and Severity > 0. If there is a match, it will change the Severity = 0 after 120 seconds. Then the delete_clear trigger clears the event.
You can disable event paring using the command line, or by setting the datasourceclearpair property in the $IMPACT_HOME/etc/<servername>_selfmonitoring.props file. Using the command line is the preferred method. The datasourceclearpair property is enabled by default.