Indicates whether the commands performed on each file are tracked so that you can “undo” as many as are specified by Undo levels. When this checkbox is selected (default), commands are tracked and can be undone. Clearing this checkbox can save you a great deal of memory usage and speed up certain operations.

When Enable undo is selected, the value entered in the Settings column indicates the maximum number of commands tracked for “undo” purposes. The default is 256. Reducing this size decreases memory consumption and speeds up certain operations.