Undo’s Maximum Size for Revit 2012

The Undo button allows users to step-backward and cancel their recent changes to the model.  Here are some helpful things you probably don’t know about it:

1. The Undo button in Revit is hard-coded to hold 100 Transactions (individual actions, such a drawing a wall) or Transaction Groups (e.g. entering a sketch mode when using the Floor tool).
2.  Transaction number 101 will cause the very first one to drop off the list (it’s a FIFO behavior: First In, First Out). 
3. New to Revit 2012, however, is that a single Transaction Group can hold as many as 10,000 undo-able actions—so theoretically you could have as many as one million items in your Undo list! 
4. You don’t have to step back one-action-at-a-time—use the drop-down arrow then scroll down as far as you want to undo, clearing multiple steps in one click.
5. After using Undo, the Redo button can recreate all (or part) of everything you just undid.  But if you cause a new transaction to be added to the Undo list, the Redo list will be completely cleared.
6. Keep in mind that there are a several actions which will completely clear out the Undo list, such as Closing and re-opening your file and unloading a Link!