When the storage allocated for changes is exhausted, UNDO recycles itself and puts up the message UNDO RECYCLED. Recycling is the process of saving the current image of the file as a new base from which to work. UNDO is then available after the next transaction. No transactions made before the recycling can be undone. This is because UNDO saves an image of the original file and keeps an incremental list of changes to that image.

If there is not enough storage to save the initial image, UNDO attempts to use the recovery file for undo processing. If recovery is off or suspended, the message UNDO SUSPENDED is shown with an alarm, and the profile status line is changed to SETUNDO SUSP. If recovery is available, the message UNDO FROM RECOVERY is shown with an alarm, and the profile status line is changed to SETUNDO REC. This affects the display but does not affect the edit profile values.

To resume SETUNDO STG, enter the SETUNDO primary command. If there is still not enough storage to hold the original copy of the file, the recycling procedure is repeated.