A recoverable session can be used to preserve your workload under exceptional circumstances such as a power failure or host failure.
Recoverable sessions can incur additional overhead because the workload must be journaled. Specifying your sessions as recoverable may not be appropriate for all types of workload, since it can take less time to rerun all the tasks in the session rather than to recover and resume them. The time it takes to rerun or recover and resume tasks in a session varies with the data size and number of tasks.