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Incrementally updated backups [message #416201] Fri, 31 July 2009 02:38 Go to next message
OraKaran
Messages: 183
Registered: March 2008
Location: United Kingdom
Senior Member
Hi,

As per my understanding we have 2 type of backups (on general level)
1) Image Copy 2) Backup sets
and the Oracle 10g Feature of "incrementally updated backups" is used for "Backup sets" where incremenatl level 1 backups are merged with incremental level 0 backups
so that the recovery time is reduced since we need to apply less number of backups.

However referring the following document
Oracle® Database Backup and Recovery Basics
10g Release 2 (10.2)
Part Number B14192-03

"At the beginning of a backup strategy, RMAN creates an image copy backup of the datafile. Then, at regular intervals, such as daily, level 1 incremental backups are taken, and applied to the image copy backup, rolling it forward to the point in time when the level 1 incremental was created"

It says "RMAN creates an image copy of datafile". Does it is different from backup set and same as Image Copy?
If it is image copy, how incremental level 1, backup sets are applied to this image copy?


Also if I have 4 pieces with 4 TAGs in my incremental level 0 backup set
TAG20090731T123114
TAG20090731T123116
TAG20090731T123116
TAG20090731T123134

Can I execute following?
backup incremental level 1 for recover of copy with tag "TAG20090731T122[B]*[/B]" database;


Thanks and Regards,
OraKaran
Re: Incrementally updated backups [message #416230 is a reply to message #416201] Fri, 31 July 2009 05:09 Go to previous messageGo to next message
ebrian
Messages: 2794
Registered: April 2006
Senior Member
There are two distinct type of incremental backups with Oracle 10g. The conventional incremental backups that work off backupsets and rolling forward image copies that work off of ??...you guessed it...image copies.

With conventional incrementals you'll have level 0 and level 1 backupsets. With rolling forward incrementals, you'll have the image copies of the datafiles and the level 1 backups.
Re: Incrementally updated backups [message #416235 is a reply to message #416201] Fri, 31 July 2009 05:23 Go to previous messageGo to next message
OraKaran
Messages: 183
Registered: March 2008
Location: United Kingdom
Senior Member
Thanks ebrian,

Quote:

With rolling forward incrementals, you'll have the image copies of the datafiles and the level 1 backups.



Now the level 1 backups in above quote are agaain image copy or backup sets?

Sorry for my (mis)understanding but I believed only backup sets can be incremental.And in above case if level 1 backup refers to backup set, original question remain :how it can be merged with image copy?

Also referring the post message #295393, i felt backupsets can be merged.

Also the "Incremental Merge" section in the following link seems referring to backup sets for merge option.

http://www.oracle.com/technology/pub/articles/10gdba/week9_10gdba.html

Thanks and Regards,
OraKaran
Re: Incrementally updated backups [message #416242 is a reply to message #416235] Fri, 31 July 2009 05:53 Go to previous messageGo to next message
ebrian
Messages: 2794
Registered: April 2006
Senior Member
The level 1 backups are backupsets that will be applied to the image copies.

I'm not sure where message #295393 is ?
Re: Incrementally updated backups [message #416248 is a reply to message #416201] Fri, 31 July 2009 06:27 Go to previous messageGo to next message
OraKaran
Messages: 183
Registered: March 2008
Location: United Kingdom
Senior Member
Thanks ebrian,

It means only for the first time I will taking backup as "image copy" and subsequently back up as "backup sets" to be merged with.

This looks fine, but what is mentioned in the article referred earlier, is we are applying level 1 to level 0.

Now Image copy can not have any level not even 0. That is little confusing.

Quote:

Incremental Merge

Let's say you have the following backup schedule:

Sunday - Level 0 (full), with tag level_0
Monday - Level 1 (incremental) with tag level_1_mon
Tuesday - Level 1 (incremental) with tag level_1_tue

and so on. If the database fails on Saturday, prior to 10g you would have had to restore the tag level_0 and then apply all six incrementals. It would have taken a long time, which is another reason many DBAs shun incremental backups.

Oracle Database 10g RMAN radically changes that equation. Now, your incremental backup command looks like this:

RMAN> backup incremental level_1 for recover of copy with tag level_0 database;


Here we have instructed RMAN to make an incremental level_1 backup and merge that with the full backup copy with the tag level_0. After this command, level_0 becomes a full backup of that day.

So, on Tuesday, the backup with tag level_0, when merged with incremental level_1 backup, becomes identical to the full Tuesday backup. Similarly, the incremental taken on Saturday, when applied to the backup on disk, will be equivalent to a full level_0 Saturday backup. If the database fails on Saturday, you just need to restore the level_0 backup plus a few archive logs to bring the database into a consistent state; there is no need to apply additional incrementals. This approach cuts down recovery time dramatically, speeds backup, and eliminates the need to make a full database backup again.



Thanks and Regards,
OraKaran
Re: Incrementally updated backups [message #416251 is a reply to message #416248] Fri, 31 July 2009 06:37 Go to previous messageGo to next message
ebrian
Messages: 2794
Registered: April 2006
Senior Member
The example you are referring to is a little confusing in understand the concept of rolling forward image copies.

Check Incrementally Updated Backups: A Basic Example or RMAN Image copy features of the Oracle 10G, which I think explains it better.
Re: Incrementally updated backups [message #416256 is a reply to message #416201] Fri, 31 July 2009 06:46 Go to previous message
OraKaran
Messages: 183
Registered: March 2008
Location: United Kingdom
Senior Member
ebrian ,

I will go throgh the links and will post in case of queries

Many thanks for your help

Regards,
OraKaran
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