PURPOSE: To evaluate performance on various conditions without stopping the operation of a system by evaluating the performance from the history of the access of an application program and spriously changed storage structure or the definition of resources.

CONSTITUTION: First of all, the history of issuing an instruction from an application program 20 under operating so as to access a table inside a data base 14 is collected and stored within prescribed time. Next, sprious change data on the storage structure of the table or the definition of resources are inputted to a performance evaluation part 10. Then, a performance parameter is calculated based on the history of the table access instruction to be stored and spriously changed conditions. In this case, the performance parameter is provided by spriously executing the table access instruction according to the history on the spriously changed conditions or the performance parameter is logarithmically calculated by using any prescribed formula. Thus, the performance at the time of changing the storage structure or the definition of resources can be evaluated without stopping the operation of the system.