not exactly sure what you mean - if you have a repair to carry out on the domestic water supply then yes it is possible to shut off the water and still have the heating running. water will not leave your heating system unless you drain it - unless you mean that you want to drain the heat exchanger in the boiler? if you are then DON'T try and run the boiler.
if running a combi system you can shut all the water off (hot and cold) centrally at the stop cock, one advantage of the combi. this should not affect your heating.