In a system including an integrated monitoring system and its monitoring target system, a technology capable of achieving detailed monitoring for a plurality of virtual servers or others by appropriately identifying the plurality of virtual servers, managing their ID information, and others is provided. The present system includes an ID managing function of performing ID management for a monitor processing for each of a plurality of virtual servers (server instances) in the monitoring target system. The ID managing function performs a processing of providing a uniquely-identifiable ID (instance ID) to each of the plurality of server instances and identifies each of the server instances by referencing the ID at the monitor processing.