Control monitoring system and computer system

A control monitoring system comprising: a control monitoring system in which a control console and a plurality of controllers are provided in a monitoring control network and communicate with each other, each of said plurality of controllers being configured as either a main system or a sub-system, thereby forming redundant systems; and a computer system which includes a gateway device connected to the monitoring control network, and a human interface device. When the gateway device changes a first request message received from the human interface device into a second request message and transmits the second request message to controllers via the monitoring control network, the gateway device determines the destination controllers on the basis of a data name indicated by the request in the first request message, and generates and outputs the second request message after verifying that the total amount of processing to be performed by each of the main system and sub-system controllers that constitute the destination controllers does not exceed the maximum processing performance of the controller.