The RTO (Recovery Time Objective) specifies the maximum tolerable period within which a system must be operational again after a failure. An RTO of two hours means the service must be available again within two hours of the outage. The RTO influences the choice of recovery strategy — from cold standby to active-active clustering. You define the RTO per system in the business impact analysis and test it regularly in DR exercises. Together with the RPO, it forms the backbone of your business-continuity planning.