Re: Undo Retention of 5 days; anyone?
- From: Kirtikumar Deshpande <kirtikumar_deshpande@xxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Wed, 11 Feb 2004 22:09:28 -0800 (PST)
Arup,
This may require a tonne of disk space. Please refer to Admin Guide Chapter 13
(I think) where an
example shows about 5 GB of undo space just for 20 minute U_R. Of course, this
depends on the
amount undo generation rate.
Most important thing is that the undo_retention period, irrespective of the
amount undo disk
space, is not guaranteed. Oracle will ignore this setting when in need of undo
space for a
transaction. Keeping the transaction alive is more important than ORA-1555
error.
Now, if you have ample disk space for this, then this is possible. But I
suggest using Resource
Manager to set undo_pool quota to limit undo space usage. So a rogue
transaction will not use the
tablespace for 5 long days.
I have done this in one of my Test/Acceptance database, where I hacked the DD
to allow 10 days of
Flashback ;-) And had to recovered data in one table that was deleted 7 days
ago!
I am at RMOUG Training Days 2004 Conf this week, and may not get a chance to
review e-mail again
till the week-end. But if you needed more information, please let me know. I
will respond when I
get back to Dallas.
Cheers!
- Kirti
--- Arup Nanda <orarup@xxxxxxxxxxx> wrote:
> List,
> I have a very unusual request from users to have UNDO_RETENTION set to 5
> days. Normally I set to
> about 5 hours, not days. Don't ask why. They have inherited a bad design that
> requires flashing
> back to 5 days ago and, no, they can't redesign it.
>
> I'm curious if anyone has actually done it, i.e setting it to a very high
> value. Any input will
> be highly appreciated.
>
> Thanks a lot in advance.
>
> Arup
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