I have also been working in a consultancy firm. Even i have been stuck on the same issue to final DCS. will u plz evaluate why Siemens PCS7 is not a reliable solution as DCS. plz give technical specs.

 

Everyone can consider there own idea of DCS. Mine is a control system domain where numerous controllers are operating in different factory situations or locations, with none being in overall control.

Any DCS system can be configured by various single PLCs networked together, and have done so in the past with Rockwell, Mitsubishi and Siemens. The tricky area is SCADA - should this have overall (operator) control or be itself split into many logical areas.

PCS7 is literally Process Control using S7 PLC family - is it DCS ? - not really but IMHO can be. However understand PCS7 is being phased out so nowadays the point may become seemingly irrelevant.