1. A method of controlling a computer system which includes a host computer and one or more storage systems coupled to the host computer via a network, the host computer including a first interface coupled to the network, a first processor coupled to the first interface, and a first memory coupled to the first processor, each of the storage systems including a port coupled to the network, a second processor coupled to the port, and a second memory coupled to the second processor, at least one of the one or more storage systems including a physical storage device for storing data written by the host computer, a physical storage area of the physical storage device being allocated to a logical storage area, wherein the first processor executes an application program stored in the first memory to execute an application job which executes data I/O in the logical storage area via the first interface; the second processor executes a management program stored in the second memory to executes a management job which executes the data I/O in the logical storage area for managing the storage systems; the method comprising: judging whether at lest one of resources of the computer system used for the data I/O of the application job is also used for the data I/O of the executed management job when performance of the application job drops below a predetermined first threshold value; and displaying information indicating the executed management job when it is judged that at least one of the resources used for the data I/O of the application job is also used for the data I/O of the executed management job.