Computer system for managing performances of storage apparatus and performance management method of the computer system

In a computer system with a DBMS running thereon, management of the performance of a storage apparatus is executed by using a performance indicator provided by a user job so as to simplify the management of the performance. For this reason, a management server employed in the computer system monitors an operating state of each system element, a response time onto a job and other information. A method for estimating a processing time is given to the management server, which issues a setting modification command based on an estimated processing time.