The growing awareness of the substantial environmental footprint of Information System has increasingly focused corporate transformation efforts on the efficient usage of Information Technology. In this context, we provide a new concept to enterprise IS operation and introduce a novel adaptation framework that harmonizes operational requirements with efficiency goals. We concretely target elastic n-tier applications with dynamic on-demand resource provisioning for component servers and implement an adaptation engine prototype. Our framework forecasts future user behavior, analyzes the impact of workload on system performance, evaluates the economic impact of different provisioning strategies, and derives an optimal operation strategy. More generally, our adaptation engine optimizes IT system operation based on a holistic evaluation of the key factors of influence. In the evaluation, we systematically investigate practicability, optimization potential, as well as effectiveness. Additionally, we show that our framework allows flexible IS operation with up to a 40 percent lower cost of operation