Re: Serializable transactions get rolled back while there are no othertransactions running?!

From: Oliver Zeigermann <oliver_at_zeigermann.de>
Date: Thu, 24 Jun 2004 17:50:41 +0200
Message-ID: <2k0bksF15k9jlU1@uni-berlin.de>

ctcgag_at_hotmail.com wrote:

> "Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote:
> 

>>Apparently, this one will be fixed in Oracle 11
>>(yes, really, that wasn't a joke).
>>
>>Could you clarify what environment or feature
>>you are thinking of when you comment on the
>>"per-table configured memory " and the need
>>to configure more of it.
>>
>>Regarding:
>>
>>>Any data that is read by a serializable tx can be altered and committed
>>>by
>>
>>another
>>
>>>tx before the first one completes, and if the first tx rereads the
>>>changed data it will still see the old values, even though the real
>>>data has been changed.
>>
>>I think that's what most people would expect of serializable.

> 
> 
> Not I.  I would expect one of the two to get a "cannot serialize" error.
> The isolation level that Oracle calls "serializable" is not truly
> serializable.  I'm not saying that that level isn't useful, nor am I saying
> that it could be made truly serializable without incurring significant
> performance penalties.  I'm just saying they probably shouldn't have named
> it "serializable" when it really isn't.

I think theoreticians call this isolation level "snapshot" and what makes it worse than "serializable" are "write skew"s.

Oliver

Using funky terms like the ones above makes me look smart, but this is just what I have found on web sites of truly smart people ;) Received on Thu Jun 24 2004 - 10:50:41 CDT