Abstract: A network data server apparatus is connected to a plurality units of PLC 3.sub.1 to 3.sub.n as well as to at least one unit of FA controller in a manner enabling bidirectional communications. Provided in the network data server apparatus are a memory for PLC enabling read/write of PLC data and a copy data list section with memory addresses from which data is copied and those at which data is copied described therein, and data copying is executed by a control means according to the memory addresses from which data is copied and those at which the data is copied.

Abstract: In a network management system comprising a plurality of manager nodes and a proxy agent node for managing network resources, an efficient network management apparatus is provided for calculating a network load, automatically adjusting monitor traffic occurrence intervals in response to the load totalizing inquiries from the managers and preventing duplicate inquiry handling, and caching the inquiry result for suppressing access to the network resources. The management traffic occurrence frequency is automatically optimized in response to the network load and essential application communication performance is prevented from lowering for enhancing processing efficiency.