"Giridhar" <gkodakalla@gmail.com> wrote in message
news:1147152845.214758.144960@j33g2000cwa.googlegr oups.com...
> Hi,
> While reading backup and recovery manual, i read the following:
> --------------------------------------------------------------------------
-------------------------------------------------------------
> transaction recovery
> Transaction recovery involves rolling back all uncommitted transactions
> of a failed instance. These are "in-progress" transactions that did not
> commit and that Oracle needs to roll back. It is possible for
> uncommitted transactions to get saved to disk. In this case, Oracle
> uses undo data to reverse the effects of any changes that were written
> to the datafiles but not yet committed
> --------------------------------------------------------------------------
-------------------------------------------------------------
>
> Can someone please explain how can uncommited transactions gets saved
> to disk.
> I assumed only commited data gets saved to disk.
>
> Thanks.
> Giridhar Kodakalla.

Since most transactions are committed and not rolledback Oracle writes
uncommitted transactions to the datafiles. So when you issue a commit then
it doesn't have to write the data to the datafiles. It does have to indicate
that the data is committed.
Jim