CARRIER PWM CONTROL OF CASCADED HYBRID NPC 3-LEVEL INVERTER AND TWO-LEVEL INVERTERS

A volume control system in a storage area network environment, which is capable of executing volume operation requests in multiple stages, and is also capable of canceling an erroneous volume operation even after the operation has been executed by the user. A volume operation request for executing run commands from the user is analyzed, and parameters for executing the volume operation request are created by a program that operates the storage apparatus. Each of the parameters is provided with an attribute indicating as to whether cancellation is possible or as to when the execution is to be performed. If cancellation of the run command is possible, a parameter for canceling the run command is created simultaneously. The run commands may be executed on the basis of the parameters after verifying by a simulation as to whether or not the various parameters created are correct. At this point, the user may select whether to execute the run commands promptly or in stages. When the user selects executing the run commands in stages, the user registers execution conditions for executing the run commands. In the event the user makes a cancellation request before the registered execution conditions are fulfilled, any of the run commands that has been executed can be cancelled by using cancellation parameters.