Re: Different backup procedure.

You MUST use archivelog mode to do hot backup.

When you do hot backups, the database is up and users are updating!

The basic hot backup script is:

     for each tablespace

          alter tablespace _______ begin backup:
          for each datafile of the tablespace

               tar, cpio, dd, .... the file

          next file
          alter tablespace _______ end backup;

     next tablespace

Since the users are updating while the backup is running, the backup is 'fuzzy'. That is, the backup files are not from a single, consistent point-in-time. So, if you restore all the database files from your hot backup, you will need to apply the redo logs (recovery) that were created during the backup. (You may need to apply even more logs, depending on the point-in-time to which you are recovering.)

This is why you need archivelog mode for hot backups: archivelog mode ensures that you still have the redo log data that you need for recovery.

Backups enable recovery. If you don't need recovery, you don't need backup!

Cold backup enables recovery to the point-in-time of the cold backup. Without archivelog mode, no further recovery is possible. With archivelog mode, you can recover to any point-in-time up to current time.

Hot backup enables recovery to the point-in-time where the hot backup terminated. Since this requires archivelog mode, you can recover to any point-in-time up to current time.

Archivelog mode enables recovery of the work since the last hot or cold backup. If you can afford to lose all work since the last backup, you don't need archivelog mode!

Archivelog mode also enables hot backup. If you can shut down your database long enough for a cold backup, you don't need hot backup.

     John

giau45_at_yahoo.com wrote:

> I keep reading on Oracle backup procedure. And I'm still fuzzy about
> hot backup and archive mode.
>
> Cold backup: shutdown all DB and do a complete copy of dbf files (as I
> understand it)
>
> How is backup work and archive log mode work ? Thank you.
Received on Fri Aug 07 1998 - 22:40:46 CDT