Re: Recovery possible?

From: Mark Malakanov <markmal_at_sprint.ca>
Date: Sat, 3 Jul 1999 11:58:46 -0300
Message-ID: <xnqf3.1416$jl.11138033@newscontent-01.sprint.ca>

May be I misunderstand. But.

What what happens when Oracle aborted?

- Instance shutdown immediately,
- No uncommited transaction does rollback.
- Unarchived redo log files stay unarchived.

What what happens when Oracle starts after this?

- Oracle roll forward all data changies from current redo log to SGA.
- Oracle rollback uncommited transactions.
- Oracle switch redo log.

All of this happens without difference of ARCHIVELOG or NOARCHIVELOG. - If ARCHIVELOG mode set, ARCH process writes unarchived redo logs to archive log.

Therefore, If you made backup of datafiles of aborted DB, your commited(!) information will saved firstly inside the current redo log file, and secondly written to archive log.
And you can roll forward from any backup (aborted or normal shutdown), or even from hot backup. All data changies saved in a set of archive log files and unarchived redo logs.

You need not turn your database to NOARCHIVELOG mode before SHUTDOWN ABORT.

Regards,
Mark Malakanov

Thomas Kyte <tkyte_at_us.oracle.com> wrote in message news:377d6cdb.1498054_at_newshost.us.oracle.com...
> A copy of this was sent to "Mark Malakanov" <markmal_at_sprint.ca>
> (if that email address didn't require changing)
> On Fri, 2 Jul 1999 21:43:07 -0300, you wrote:
>
> >
> >Thomas Kyte <tkyte_at_us.oracle.com> wrote in message
> >news:3786d1c5.150939018_at_newshost.us.oracle.com...
> >
> >> If you shutdown normal or shutdown immediate yes.
> >>
> >> If you shutdown abort and back it up -- you will not be able to roll
this
> >backed
> >> up instance forward.
> >
> >The rollback event does not appears when you make SHUTDOWN ABORT.
> >In other it looks like SHUTDOWN IMMEDIATE.
> >The transaction information is written in the current redo log file any
way,
> >was it commited or not.
> >
> >Therefore you can backup datafiles shutdowned rudely.
>
> but, as i said, you you will NOT be able to roll instance forward ("using
> archived redo logs" -- this part was implied but not explicitly stated.
you
> will only be able to recover the instance to the point in time of the
BACKUP -
> your archived logs are useless).
>
> If you have a database in archive log mode -- and you do a backup of a
shutdown
> abort database -- you may as well TURN OFF archive log mode.
>
> If you have a noarchive log mode database, go ahead, shutdown abort and
backup
> everything -- no problem.
>
> if you have an archive log mode database and you shutdown abort -- you are
just
> wasting your time.
>
> >At next start Oracle will ARCH will switch redo log and write the recent
> >current redo log file into archive log. You can roll forward this archive
in
> >the future.
> >Of cource, uncommited transaction will be rollbacked after rollforward.
> >
> >Regards,
> >Mark Malakanov
> >
> >
>
>
> --
> See http://govt.us.oracle.com/~tkyte/ for my columns 'Digging-in to
Oracle8i'...
> Current article is "Part I of V, Autonomous Transactions" updated June
21'st
>
> Thomas Kyte tkyte_at_us.oracle.com
> Oracle Service Industries Reston, VA USA
>
> Opinions are mine and do not necessarily reflect those of Oracle
Corporation Received on Sat Jul 03 1999 - 09:58:46 CDT