Re: Backup questions

"Matthieu Darnet" <darnet_at_club-internet.fr> wrote in message news:99b9do$lua$1_at_front9.grolier.fr...
> Hi,
>
> <vikasa_at_despammed.com> a écrit dans le message news:
> sl2ibt4pm54th4q8ig5be9jlcghs3luppb_at_4ax.com...
> > Would appreciate help with the following backup/recovery related
> > issues:
> >
> > 1. During online backup, when a tablespace is marked as BEGIN BACKUP,
> > any changes to that tablespae are recorded in the redologs. When the
> > END BACKUP is issued, does Oracle read the redologs and apply these
> > changes to the actual datafile(s) of the tablespace? Or does it just
> > stay in the redolog?
> When the END BACKUP is issued, all the changes made during backup are
> applied on the tablespace.
>

Total rubbish. Hot backup does not prevent normal I/O to the datafile. If it did, we wouldn't have to swamp the redo subsystem with block sized redo trying to prevent block fracturing (which only happens when the O/S is grabbing bits of Oracle blocks *whilst the rest of the block is being updated*.

HJR
> >
> > 2. After issuing a BEGIN BACKUP and during copying the tablespace's
> > datafile, there is a disk failure and the datafile is lost. How does
> > one recover in this case?
> You would need to restore a previous backup of this file and apply all
> archived logs since then.
> The begin backup doesn't help you there.
>
> >
> > 3. If I need to recover only a few datafiles and not the entire
> > database, I would do RECOVER DATAFILE <datafile>. What happens in this
> > case? Does Oracle ignore the redo entries which pertain to the other
> > datafiles?
> Yes, it only applies changes made to this particular tablespace, all the
> other changes are ignored.
>
> >
> > Under what situation would I need to do ALTER DATABASE DATAFILE <file>
> > OFFLINE DROP?
> If you have moved all the objects from that file to another one, and you
> don't want it anymore.
> Maybe also in case of a transportable tablespace, but the command might be
> issued at tablespace level (i'm not sure).
>
> >
> > Once I do this, how can I bring the datafile online again?
> You can if it is a transportable tablespace. Else, you would have do
> recreate the datafile, but you would lose all data.
>
> >
> > Thanks...
>
> Hope I helped.
>
> Matthieu Darnet
>
>
Received on Thu Mar 22 2001 - 03:20:51 CST