Re: Backup & Restore

From: Brian Peasland <dba_at_nospam.peasland.net>
Date: Tue, 18 Sep 2007 11:10:13 -0500
Message-ID: <46efec6e$0$16386$88260bb3@free.teranews.com>

vitalisman_at_gmail.com wrote:
> On Sep 18, 4:43 pm, Brian Peasland <d..._at_nospam.peasland.net> wrote:
>

>> Have you looked at Incrementally Updated Backups in 10g? With IUB, you
>> only have to restore the level 0 and then *one* level 1 backup and the
>> redo logs.

>
> Hi Brian,
> I don't know if it was due to your phrasing but your explanation looks
> strange to me.
>
> Having to restore just 1 level-1 backup after 1 level-0 backup is
> guaranteed with cumulative incremental backups, available with 9i.
>
> I have never used IUB yet, but when you want to restore, you don't
> have to restore any level-0 backup according to the doco, only one
> level-1 backup.
> I don't think IUB is a great thing because of the disk space needed.
> And if the database is not that huge, why bothering with incremental
> stuff?
>
> Jerome
>

Actually, IUB can save you more disk space. You won't have multiple level 1 backups lying around. The level 0 is "updated" (hence the term Incrementally Updated) with changes from the previous level 1. The following is a good paper discussing IUB's.

http://www.nyoug.org/Presentations/SIG/DBA/10grman.pdf

The big difference between IUB's and cumulative incremental backups is that IUB's update the level 0 copy and the only level 1 denotes the changes since the level 0. When you run a new level 1, the level 0 gets updated with the old level 1 info and a new level 1 is created.

The cumulative backups keep the level 0 the same. The level 1 just holds all changes since the level 0. If every block changes since that level 0, the level 1 could be as large as the level 0 backup.

If your database is small, then incrementals may not be of any interest to you. If your database is small, then why not just perform a full backup every time? Incremental backups were not created for small databases. They were created to reduce the backup window of large databases.

Cheers,
Brian

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Brian Peasland
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Received on Tue Sep 18 2007 - 11:10:13 CDT