[ZODB-Dev] non-transactional undo

[Tim Peters]

[Toby Dickenson]
> ...
> This is the only place that FileStorage writes somewhere other than
> the tail of the file,

I believe that every time a transaction is committed to a FileStorage, a
status byte in a header gets rewritten at the end of the write (to say that
the write completed successfully).  In particular, if you make a copy of a
live FileStorage, the last transaction copied may be in an incomplete state
because of this.

> so the possibility of a non-transactional undo complicates any backup
> schemes.

Correct backup schemes involving a live storage are likely complicated
regardless.