Oracle Rman incremental


I have a question I think I know the answer to but want some clarification. At present I do full backups everynight of my 3 oracle databases the biggest of the 3 is 250gb in size. I know that I should use incremental backps which will speed up my backups and also keep the size of these backups down in size but what I am fearing here is what happens if say:-

1. Full backup taken on say the Friday night then incremantels taken everyday for the next 7 days.

If for some reason a corruption happens to the backups and there is a problem with the 4th days backup like they are deleted by mistake what happens after this does rman compensate I am not sure.

Any one out there can answer this



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It depends on the incremental level. In your example if you take back of incremental level 0 means. It will take  backup of all changed data since Friday. If you have to restore you have to restore Friday + ONE DAY.
It means if you want to restore database to Sunday then you have to restore Friday + Sunday data only.
This mean if you are missing / deleted Saturday incremental back then it will not have any impact. But you will not able to restore for Saturday.
But if your Incremental level is 1 then you have to restore Full Backup + Next Day + Next Day + ....Until the day you want to restore. In this case if you deleted any middle day backup. You will from that day to now.

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DarrenJacksonAuthor Commented:

Thanks for this..

Sooo if I can live with the fact if I loose a days incremental backup I wont be able to restore that days but have the security that it wont affect any other days backup then level 0 is the option

But if I cant then I need to go down the level 1 option but run the risk that if I loose a days incremental I will loose all potential restore from that point for the remaining week

if this about right

I know everything has pros / cons and it is just about weighing these up to come to a solution

Yes you are right.
Level 0:
FULL BACKUP----------------------SATURDAY
FULL BACKUP------------------------------------SUNDAY
FULL BACKUP-----------------------------------------------MONDAY

Level 1:
FULL BACKUP---------------------SATURDAY

Hope you understand this easily.
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One more thing:
Its better if you study Oracle Backup and Recover Advance User Guide also.
I want to clarify something:
Incremental Classification:
 Incremental backups are classified by level. A LEVEL 0 incremental backup performs the same function as a full backup in that they both back up all blocks that have ever been used. The difference is that a full backup will not affect blocks backed up by subsequent incremental backups, whereas an incremental backup will affect blocks backed up by subsequent incremental backups.

Incremental backups at LEVEL1 back up only blocks that have changed since previous incremental backups. Blocks that have not changed are not backed up. An incremental backup can be either a differential incremental backup or a cumulative incremental backup.
DarrenJacksonAuthor Commented:

Thanks again and yes I will study this in more depth and thanks for the info

DarrenJacksonAuthor Commented:
Very helpful thank you
slightwv (䄆 Netminder) Commented:
Even though you've already closed this out I wanted to have you look up

Rolling Incremental backups:

4.4.3 Incrementally Updated Backups: Rolling Forward Image Copy Backups

and Block Change Tracking:
4.4.4 Improving Incremental Backup Performance: Change Tracking

Rolling incrementals basically go:
initial backup:  level 0
Do a level 1.
Take level 1 and apply back to level 0.

This way your level 0 is only ever 1 day old.
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