Re: backup UNDO Tablespace (dba_undo_extents)
- From: Roger Xu <wellmetus@xxxxxxxxx>
- To: Jeremiah Wilton <jwilton@xxxxxxxxxxxxx>
- Date: Tue, 15 Dec 2009 13:35:24 -0600
Thank you all. By the way, here is an example from Tom:
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:5669213349582
On Tue, Dec 15, 2009 at 12:34 PM, Jeremiah Wilton <jwilton@xxxxxxxxxxxxx>wrote:
> Roger,
>
> As Mark P. pointed out, RMAN in 10g does not back up regions of datafiles
> that have never been used. However, it seems like at some point the whole
> tablespace filled with undo segments, then some segments shrunk or went
> away. I think RMAN will back up all blocks that have ever been part of any
> segment.
>
> If you want to make the backup small again, in line with the current
> allocation of undo, then switch to a new undo tablespace and drop the old
> one. This will work until someone does a giant transaction again!
>
> Or you could take the other advice someone gave and never back up undo
> tablespaces. Maybe skip SYSTEM too! (***JUST KIDDING***).
>
> Regards,
>
> Jeremiah Wilton
> Blue Gecko, Inc.
> http://www.bluegecko.net
>
>
> On Dec 15, 2009, at 9:17 AM, Roger Xu wrote:
>
> This thread is nothing to do with the reason why we need to backup undo.
> I just want to backup the undo segments which are required for recovery but
> not the entire undo datafile. (I know 11g skips commited before image but I
> am at 10g.)
>
> On Tue, Dec 15, 2009 at 11:07 AM, MacGregor, Ian A. <
> ian@xxxxxxxxxxxxxxxxx> wrote:
>
>> The undo tablespace is required for database recovery
>>
>> On Dec 15, 2009, at 8:51 AM, "Guillermo Alan Bort" <
>> cicciuxdba@xxxxxxxxx> wrote:
>>
>> Short answer... don't take a backup of the undo tablespace... it's not
>> required for database recovery.
>>
>> On Tue, Dec 15, 2009 at 1:20 PM, Roger Xu < <wellmetus@xxxxxxxxx>
>> wellmetus@xxxxxxxxx> wrote:
>>
>>> We have only one datafile (20 GB) in the undo tablespace.
>>> When I ran RMAN backup of this datafile, it created a 20GB backupset
>>> file.
>>> I query dba_undo_extents and it shows less than 80 MB used.
>>> ...
>>> Any explanation? ...
>>>
>>
>
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