Because rollbacks can involve millions or billions of rows, competing for CPU and other system resources, rollbacks can impact system performance. Rollbacks can keep locks on affected tables for hours or days until the rollback is complete. During a rollback, a trade-off occurs between overall system performance and table availability.
How RollbackPriority affects performance is not always straightforward, and is related to the Priority Scheduler configuration, job mix, and other processing dynamics. The RollbackPriority setting should only be changed after full consideration of the performance consequences:
The default setting of FALSE is especially appropriate when rollbacks are large, occurring to critical tables that are accessed by many users. It is better to complete these rollbacks as quickly as possible to maximize table availability.
A setting of TRUE is appropriate when rollbacks are typically smaller, occurring to smaller tables that are less critical, and less extensively used.
Regardless of the RollbackPriority setting, rollbacks are never subject to CPU limits: