You can initiate checkpoints for a task by using the BR (Breakout) system command. This feature is designed to allow you to checkpoint tasks when an external condition prevents execution from continuing. For example, checkpointing a task just before halt/loading the system preserves the work done up to that point.

The BR command, if it is completed successfully, has the same effect as a CHECKPOINT statement in a program. All restrictions that apply to a programmed checkpoint also apply to an operator-initiated checkpoint. For example, the task must have been initiated from a WFL job and must not have any offspring. The task must be written in ALGOL or COBOL74. For details about these restrictions, refer to Restrictions on the Use of Checkpoints earlier in this section.

The programmer is responsible for designing a task to recover data file contents and libraries after a restart. It can be difficult to design such recovery mechanisms without knowing exactly when the checkpoint will take place. You can overcome this difficulty through the use of the BRCLASS task attribute. This task attribute specifies whether the task currently allows an operator-invoked checkpoint.