Re: student question: incremental backups (level 0 and level 1)

From: Holger Baer <>
Date: Wed, 25 Jun 2008 19:02:29 +0200
Message-ID: <g3ttn7$ng3$> schrieb:

> Comments embedded.
> On Jun 25, 4:58 am, (obakesan) wrote:

>> Hi
>> so far my oracle experience has been on 8i with only PL/SQL development on 9
>> and later.
>> I'm just going through some questions in preparation for a 10g Admin 1 exam
>> and find (among others) a question for which the answer seems to be less than
>> right. Of course I can simply memorize the answer, but in the interests of
>> developing knowledge (rather than simply passing exams) I thought I'd seek
>> some suggestions here.
>> The question poses: You perform differential incremental level 1 backups of
>> your database on each working day and level 0 backups on Sundays. which two
>> statements are true about the differential incremental backups.
>> the answer I have issue with is: the backup performed on sundays contains all
>> the blocks that have everbeen used in the database.
>> I would have thought that it is possible for blocks to be used and then become
>> free, these blocks should then not need backing up ... no??
> No.  They are below the HWM so they do get backed up.  Any block below
> the HWM has the potential to contain data.  Thus, all blocks below the
> HWM are backed up.

>> I'd have thought
>> it was also possible that eventually (despite being used and freed) this could
>> eventually encompas every block in a datafile.
> It could.  And the issue with that is?

>> thus the word EVER seems to be making this a wrong answer (which it is not
>> according to my review software).
> It's wrong only in your mind.  It's correct in terms of the concepts
> and functionality of RMAN.

>> I'd be happy to learn what I've overlooked on this ... thanks :-)
>> See Ya
>> (when bandwidth gets better ;-)
>> Chris Eastwood
>> Photographer, Programmer Motorcyclist and dingbat
>> blog:
>> please remove undies for reply
> David Fitzjarrell

The documentation is a little bit clearer (

Multilevel Incremental Backups

RMAN can create multilevel incremental backups. Each incremental level is denoted by a value of 0 or 1. A level 0 incremental backup, which is the base for subsequent incremental backups, copies all blocks containing data. The only difference between a level 0 incremental backup and a full backup is that a full backup is never included in an incremental strategy.


The important point to note:
- a level 0 incremental backup copies all blocks containing data

This does not mean all blocks that *ever* contained data, think of truncate table for example. So the OP is right to express his doubts about the wording, even if it's not in the sense he originally meant. Another example: drop a table/index/partition and you're likely to to have lots of blocks that once contained data but now don't. They shouldn't (and to the best of my knowledge don't) get backed up.

Holger Received on Wed Jun 25 2008 - 12:02:29 CDT

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