Good day All,
You do not give an indication of the size of your DCS system. I have written quite a few DCS system qualification documents and actually audited all the DCS suppliers on behalf of The big P. Because a DCS will be handling "critical data" the regulators will classify it as requiring "full life cycle validation". This is intensive validation and requires full documented history of the software, virtually - from concept to commissioning.
It is almost impossible to accomplish this without the full cooperation of the original software constructors/writers.
Validation Online's website carries extensive guidance information on the construction of cGMP protocols plans and others, but unfortunately DCS systems are usually pretty unique, very large and somewhat complicated requiring large authoring teams producing completely bespoke documents.
I am of course assuming that you are going to use the DCS within the cGMP environment - if not please discard all I have said.
Regards
Alex