> > > > You mean it is restored in session that is running the transaction ?
> >
> > Depends on what you mean with restored. It first reads the heap page,
> > sees that it needs an older version and thus reads it from the "rollback segment".
>
> So are whole pages stored in rollback segments or just the modified data?
This is implementation dependent. Storing whole pages is much easy to do,
but obviously it's better to store just modified data.
Vadim