Re: Table updates during hot backups

"Neil Cudd" <neil_at_cudd.demon.co.uk> wrote in message news:967210162.9931.0.nnrp-03.c2de6f3d_at_news.demon.co.uk...
> Would I be right in saying that all changes made to a table in a specific
> tablespace, whilst that tablespace is in backup mode, are held in the
 online
> redo logs and applied only when the tablespace is bought back online (End
> Backup) ?

No, that's not correct.

The point about 'hot backup' is *not* that somehow changes are not made to datafiles, but that they can be made any time, and yet we can still reconstruct the entire file from the time the backup started. The trick to doing that is that any change you make to data in a block, no matter how trivial, causes the ENTIRE block's contents to be written to the Redo Logs. Nevertheless, if DBWR suddenly gets it into its head to flush the buffer cache, it will do so as normal.

>
> If this is not the case, how are changes applied to the tablespace at the
> End Backup ?

Nothing really happens at the 'end backup' stage, except that Oracle will no longer generate block-size Redo for that tablespace. It's back to the 'before' and 'after' images of the actual data you are changing.

>
> If you could refer me to any reference material on this subject (the
 Oracle
> Manuals are a little light on this subject), it would be appreciated.
>

You might look at
http://www.geocities.com/howardjr2000/backup_and_recovery.htm, and download the 70-page document I've done for backup and recovery courses there. It might not be the technical approach you're looking for, though.

Regards
HJR
> Thanks and regards,
>
> Neil Cudd.
>
>
>
>
Received on Fri Aug 25 2000 - 17:04:02 CDT