a relay and a data processing method are provided . the relay includes : a detection unit for classifying and detecting event oriented monitoring data and non - event oriented monitoring data from monitoring data ; a storage unit for storing the detected monitoring data ; a communication unit for receiving a request signal of the monitoring data from a monitoring device and transmitting corresponding monitoring data in response to a transmission request signal of the monitoring data ; and a control unit for extracting event oriented monitoring data from the monitoring data and performing a control to transmit the monitoring data requested from the monitoring device .