Re: RMAN: What blocks are backed up with a full backup?

I should have stated that this is Oracle 8.0.5, if that makes a difference. After posting the questions, I went to Metalink and found some conflicting informaiton, but the consensus seemed to be that it was unrelated to the HWM of the tables. For example, after dropping a table, all the blocks were still being backed up.

And as I said, for some tablespaces, it backs up many more blocks than are below the HWM blocks of the tables and in other cases it backs up fewer blocks than those below the HWM.

My current thinking is that the best way to reduce the backup size is to resize the datafiles as small as possible and then resize them back to the original size. This should reduce the size some, but I don't think there is any way to tell how much.

To get the maximum reduction, we could export...receate tablespaces...import, but it's not worth that much effort.

Keith

• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Thursday, April 03, 2003 3:23 PM

> Actually this is how RMAN works. It writes all blocks up to the HWM of a
> given table,
> even empty ones. So, if your HWM is artifically high, you will encounter
> backups
> that are larger than they need to be.
>
> Oracle9i RMAN Backup and Recovery.... On bookshelves now!
>
> RF
>
>
> -----Original Message-----
> To: Multiple recipients of list ORACLE-L
> Sent: 4/3/2003 11:19 AM
>
> Keith
> Here is my understanding (don't rely on this one). When Oracle
> allocates
> tablespace, the disk blocks are cleared. My interpretation is that when
> RMAN
> encounters a clear block, it doesn't write it to the backup piece. I
> don't
> think it spends a lot of time trying to figure out above HWM and such.
>
> Dennis Williams
> DBA, 40%OCP, 100% DBA
> Lifetouch, Inc.
> dwilliams_at_lifetouch.com
>
>
> -----Original Message-----
> Sent: Thursday, April 03, 2003 10:44 AM
> To: Multiple recipients of list ORACLE-L
>
>
> Our RMAN backup is backing up much more than the actual data blocks when
> doing a full backup. I know that it backs up all blocks that have "ever
> been
> used", but I'm trying to figure out exactly what that means. My first
> thought was that it backs up all blocks below the HWM, but I analyzed
> the
> tables and that is not the case.
>
> Sometimes it backs up more blocks than exist below the HWM for the
> tables
> and sometimes it backs up fewer blocks than those below the HWM.
>
> We are doing this to determine what we can do to reduce the size of the
> backup.
>
> Anyone have an idea how this works?
>
> Keith
>
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: DENNIS WILLIAMS
> INET: DWILLIAMS_at_LIFETOUCH.COM
>
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Keith Moore
  INET: kmoore7_at_jcpenney.com

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