Before performing an SRDF Failback operation, it is crucial to stop accessing the R2 devices to ensure data consistency and avoid potential conflicts during the failback process. Once access to the R2 devices has been halted, the failback command can be executed. After the command has successfully run, access to the R1 devices can be resumed. This ensures a smooth transition and data integrity. Therefore, the most appropriate action is to stop accessing the R2 devices, run the command, and then start accessing the R1 devices.