Repalce Field Contents isn't undoable.
That is the reason why we always say to experiment that command AFTER making a backup.
Your english was good enough to give me the bad news.Many thanks. I wonder if it is technically impossible for FM to write this into a future version.
I wouldnt think it technically impossible, but more so perhaps impractical..
Lets say you did a replace field contents on 2 million records.
Filemaker would have to temporarily store all of the original data somewhere, just in-case you did decide to hit 'Undo', then what about Redo, it would have to store the data again, during the Undo process just in-case you hit Redo..
As suggested its probably best to take this upon yourself, before mass editing any records in such a way, perform a quick save as copy, or even export of the data before hand. Its something which soon becomes second nature, especially after making the mistake once.. :-) I've been there too.