A DCS is what runs a refinery, a chemical plant or a power station. Control is spread across many controllers close to the equipment, with a plant-wide network linking them to engineering and operator stations. Compared with a PLC plus SCADA setup, a DCS is delivered as one integrated system with a common database, consistent alarm handling and tooling for complex regulatory control loops.
Vendors of DCS platforms have added OPC UA servers, historians and cloud connectors, making them part of the industrial IoT. Change is slow and deliberate, because these plants run for decades and any modification is a safety matter; IEC 62443 zoning is standard practice when external connectivity is added.
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