YAWL is build out of several independent web services. The two most important web services of a YAWL system are the YAWL Engine, responsible for actual workflow execution and state management, and the YAWL Resource Service, that manages information about the organisation (participants, roles, positions, etc.) and stores the work queues for each participant.
In almost every use case of a workflow management system like YAWL, it is crucial to retain the state of all managed workflows in any case. Usually there are multiple long-living workflows inside the system, loosing information about their state leads to a lot of work and may even result in restarting the case from scratch. Unfortunately every system may crash due to e.g. undiscovered errors, hardware failure or power outage. Then it should at least be possible to roll back the whole system to a consistent state some time before the crash occured. Therefore a consistent backup of the complete YAWL system should always be kept at a safe place. Please note that this backup must contain the data of all YAWL web services (e.g. Engine and Resource Service) at the same state.
There is now a tutorial available at YAUG describing how to backup your running YAWL system.