1. A computer system, comprising: a storage apparatus coupled to a host computer via a network; and a storage management computer configured to access the storage apparatus and the host computer, wherein the storage apparatus comprises a storage unit for storing data read/written by the host computer and is configured to provide the host computer with a storage area of the storage unit as one or more volumes, wherein the storage management computer comprises a first memory for storing task information comprising contents of an operation process performed on the storage apparatus, and a scheduled starting time and a scheduled termination time of a process, and, when a first task information is stored in the first memory, when resources used in the process of a second task information stored in the first memory are the same as resources used in the process of the first task information, the storage management computer is configured to compute times required for executing the first task information and the second task information, based on a time during which the execution times of the processes of the first task information and the second task information conflict with each other; wherein, when the execution times of the processes of the first task information and the second task information conflict, the storage management computer is configured to determine whether each of the processes of the first task information and the second task information is completed by the scheduled termination time for the each process; and in response to the determination that at least one of the processes of the first task information and the second task information is not completed by the scheduled determination time as a result of the computation of the times required for executing the first task information and the second task information conflicting, the storage management computer is configured to change the scheduled starting time so that a time for executing the process of the first task information does not conflict with a time for executing the process of the second task information, wherein the storage management computer is configured to: acquire contents of a configuration change performed on the storage apparatus; update contents of task information stored in the first memory and related to the configuration change; compute the times required for executing the processes of the first task information and the second task information by taking the updated task information as the first task information; and change a starting time so that a time for executing the process of the updated task information as the first task information does not conflict with the time for executing the process of the second task information, when at least one of the processes of the first task information and the second task information is not completed by the scheduled termination time as a result of the computation of the times required for executing the first task information and the second task information.