A data processing apparatus includes a processor that executes a procedure. The procedure includes: acquiring a plurality of events that have issued in a management-target device, storing each of the plurality of acquired events in an event storage unit, and acquiring specifying data that specify an important phenomenon key event from the plurality of events stored in the event storage unit; acquiring events in sequence from a front position of the event storage unit, and performing first processing on the acquired events according to a processing condition; performing second processing according to the processing condition on events of an important event group, the important event group including the important phenomenon key event and an event related to the important phenomenon key event; and appending completion information to the acquired important phenomenon key event in the event storage unit.