1. An operations management apparatus comprising: a correlation model storing unit which stores a first correlation model including one or more correlations detected for one or more pairs of metrics in first plural metrics; and a correlation model updating unit which, in the case that one or more metrics are added, detects a correlation for each of one or more pairs of metrics obtained by excluding said one or more pairs of metrics in first plural metrics from pairs of metrics in second plural metrics including said added metrics and said first plural metrics, and generates a second correlation model by adding the detected correlation to said first correlation model.