To provide an on-demand client service system including a virtual server using a VM (virtual machine), and a management method and a program therefor.

A server management means 11 which receives a server activation request with designation of a specific server confirms the VM state corresponding to the designated server. If no target VM is present, a VM Host least affecting the system load is selected to perform formation and activation of VM. If the VM is present and it is in a stopped state, the VM is activated. If the VM is present and it is in an activated state, instruction to the VM or the server is not performed. According to this structure, since server increase/decrease, activation or stopping is performed in conformation to the using state of a client terminal, the power consumption on the server side can be reduced.

COPYRIGHT: (C)2008,JPO&INPIT