Re: Are 9i incrementals realy incremental....

Pete's wrote:
> oracle_man_at_yahoo.com (rich) wrote in message news:<56f4f26c.0411171456.2bf2a10f_at_posting.google.com>...
>

>>According to most docs:  RMAN incremental backups only backup the data
>>blocks that have changed since the last incremental.
>>
>>I don't believe it.  I do believe it probably backs up the data files
>>that have changed since the last incremental,but NOT block changes.
>>
>>Anyone want to challenge this?
>>
>>Please send email to rheadrick_at_monster(REMOVE_ME).com

Please. Can we get a little precision and accuracy in this discussion?

First, a level 0 backup and a full backup are two different things as far as RMAN is concerned. Both happen to include all blocks (except never-used ones), and therefore both would be identical in size and content. But a level 0 backup can be part of an incremental strategy, and a full backup cannot. That is, a level 1, 2, 3 or 4 incremental backup cannot use the full backup as the baseline from which to assess what has changed and therefore what needs backing up.

Secondly, a level 1 incremental can use a level 0 incremental as it's baseline. True enough. But it can also 'compare notes' with another level 1. And a level 2 can compare notes with a level 2 or a level 1 as well as a level 0.

So: your statement that "it's only the changed blocks from the last full backup" is totally incorrect.

Also, you haven't mentioned incremental cumulative backups. A level 3 cumulative can compare notes with a level 2, a level 1 or a level 0, but not another level 3. You go on to mention it, sure enough. But the description you give is vague, and you are still confusing level 0 and full backups.

HJR
> For
> example, I backup a 30 GB db via a full backup on the weekend and then
> cumulative incrementals for the other days. For those days, it's
> approx. 20 MB to 30MB per day that changes on this DB. So Monday it
> would backup 30M, Tue. 60M, Wed. 90M ..... so on & so forth. The key
> here is to run a full backup regularly whether it's a hot or cold.
> Don't believe it, try it.
>
> HTH,
> Pete's
Received on Thu Nov 18 2004 - 14:46:08 CST