That depends on the relationship. Some D/s relationships don't involve any pain at all where others can revolve around nothing but pain ... for example, I once had a service sub, who did chores, etc ... and he never experienced pain from me.
In my case ... I get off on pain ... so my Master would never use it as a means of punishment for me. Instead, he would ignore me or leave me in the cage ... because that would upset me in place of pain. As a reward I might receive pain that would leave bruises (which I love) or he might do something special ... like give me a massage or let me wear pjs to bed.