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From: cpiodumpv on 2 Mar 2006 14:43
on 9ir2

say I have a table A and B. A contains 6 million records that need to
be updated. This is in a data warehouse.

I want to.
truncate B.
alter table B nologging

insert /*+append*/ into B select < do update on A here>.

I understand that this will generate some redo but will it generate any
UNDO?

-thanx

From: HansF on 2 Mar 2006 15:06
On Thu, 02 Mar 2006 11:43:08 -0800, cpiodumpv wrote:

> on 9ir2
>
> say I have a table A and B. A contains 6 million records that need to
> be updated. This is in a data warehouse.
>
> I want to.
> truncate B.
> alter table B nologging
>
> insert /*+append*/ into B select < do update on A here>.
>
> I understand that this will generate some redo but will it generate any
> UNDO?

Undo is used to roll back a transaction. If NO undo was generated, you
would not be able to undo the insert if something went wrong.

Not a whole lot of undo will be generated. And that undo will, in turn,
generate it's own redo.

(Yes, you need it. Suppose the system crashed in the middle of the insert
.... without it, the instance would not be able to get itself to some sort
of consistent state just to be able to open up.)

--
Hans Forbrich
Canada-wide Oracle training and consulting
mailto: Fuzzy.GreyBeard_at_gmail.com
*** Top posting [replies] guarantees I won't respond. ***

From: cpiodumpv on 2 Mar 2006 15:23
according to the expert no undo will be generated.

http://asktom.oracle.com/pls/ask/f?p=4950:8:10610603236013031632::NO::F4950_P8_DISPLAYID,F4950_P8_CRITERIA:6407993912330

From: Mladen Gogala on 2 Mar 2006 21:26
On Thu, 02 Mar 2006 11:43:08 -0800, cpiodumpv wrote:

> truncate B.
> alter table B nologging
>
> insert /*+append*/ into B select < do update on A here>.
>
> I understand that this will generate some redo but will it generate any
> UNDO?

And just why wouldn't it generate undo?

--
http://www.mgogala.com

From: Holger Baer on 3 Mar 2006 05:06
cpiodumpv(a)gmail.com wrote:
> according to the expert no undo will be generated.
>
> http://asktom.oracle.com/pls/ask/f?p=4950:8:10610603236013031632::NO::F4950_P8_DISPLAYID,F4950_P8_CRITERIA:6407993912330
>

According to the expert, no undo will be generated *IF USING NOLOGGING* option.
Try to read and understand what you cite.

Regards,
Holger
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