One embodiment includes a system for application-layer monitoring of communication between one or more database clients and one or more database servers. For example, the user may be prompted to elicit supplemental information relating to the query, or provided other feedback. The first power mesh connects first power supply voltage pads to one another. Therefore, the abnormal injector out of the two injectors is specified using a learning value of an air-fuel ratio feedback correction value based on an output of an exhaust gas sensor.