Re: Why is undo backed with redo for GTT

From: Rene Nyffenegger <rene.nyffenegger_at_gmx.ch>
Date: 2 Mar 2003 14:32:46 GMT
Message-ID: <b3t4me$1pkgn1$1@ID-82536.news.dfncis.de>

> Hello!
>
> Rollback information needs to be stored, for example for rolling back to a
> savepoint.
> Rollback information is stored in rollback segments, which are stored in
> normal/undo tablespaces.
> Changes to normal/undo tablespaces are normally logged - so far Oracle
> hasn't made a separate mechanism for handling DML on GTTs.
>
> That's my understanding. In the future it could change..

Tanel,

that's exactly my understanding as well, but the question was more if there is any cogent reason why redo is generated. If that could change in the future, do we live with a less than optimal solution at the moment?

Rene Nyffenegger

>
> "Rene Nyffenegger" <rene.nyffenegger_at_gmx.ch> wrote in message
> news:b3svke$1oju4r$1_at_ID-82536.news.dfncis.de...

>> Hello
>>
>> One of the benefits of global temporary tables (gtt) is that it does not
>> generate as much redo as 'normal' tables (See also a paralell thread on
>> c.d.o.s). However, ggt's do generate undo which is backed by redo. Now, I

> do

>> understand why the undo is necessary, but I don't understand why this undo
>> must be backed by redo. In case of a crash, only the structure of the gtt
>> must be recovered, not its content. So, it seems to me, that there is
>> nothing to be rolled back on the ggt, hence the undo generated for the ggt
>> needs not be recovered.
>>
>> What am I missing?
>>
>>
>> Thanks
>> Rene Nyffenegger
>>
>>
>>
>> --
>>   no sig today
>>
>>

>
>

-- 
  no sig today

Received on Sun Mar 02 2003 - 08:32:46 CST