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Re: changing the isolation level

From: Galen Boyer <galen_boyer_at_yahoo.com>
Date: 4 Feb 2007 10:54:22 -0600
Message-ID: <uy7ndofes.fsf@rcn.com>


On Sun, 04 Feb 2007, lehmannmapson_at_cnm.de wrote:

>>> Think of a script, that generates invoices montly. Lets say
>>> you have a average volume of $1000 dollar. So if a run of the
>>> script in the next month just returns a volume of $200 you can
>>> be pretty sure, that something has gone wrong. But if you
>>> cannot see this until you confirmed all the stuff, then it is
>>> too late to revoke it.
>> Not at all. Surely you don't think Oracle eBusiness Suite
>> financials and
>> the many banks using Oracle are overwhelmingly choosing Oracle if the
>> architecture can't handle this. There are many possible solutions.

>
> This was just an example! The point is: There are scenarious,
> where you need to read "dirty" uncommitted data.

When?

> Don't try to think all people have just that one simple business case
> where everything can be managed within on transaction by one process!
> Think of heterogenous systems where one specialised system can change
> data but it cannot commit until another specialiced system reads the
> data and performs whatever with it.

What? Then stage is somewhere, have the first session read and give the data to the 2nd process. There is never a reason to prematurely commit data.

>>> Sybase supports all levels of isolation, so when I read that
>>> Oracle doesn't allow a certain isolation level it just sounds
>>> like a lame excuse for a missing feature.
>> You are incorrect. They do not exist because they are
>> unnecessary. You need to stop trying to force Oracle into your
>> current mental model (Sybase-centric) and learn how Oracle
>> works. Start with Tom Kyte's books and the docs at tahiti.oracle.com.

>
> Thanks, I already own several useful Oracle books and my problem
> is neither a mental problem nor a Sybase one. Sybase doesn't
> force me to read uncommited data, it _allows_ me to do that
> (because I need it in my business case). And the model isn't bad
> because it works with Sybase. Sybase just performs perfectly
> according the isolation level I'm free to set, even not showing
> uncommited data if I want, while Oracle doesn't.

No, READ_UNCOMMITTED is around because of inferior architectures. There is never a business case to read some other process's uncommitted data.

-- 
Galen Boyer
Received on Sun Feb 04 2007 - 10:54:22 CST

Original text of this message

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