Re: changing the isolation level

From: DA Morgan <damorgan_at_psoug.org>
Date: Mon, 15 Jan 2007 10:20:55 -0800
Message-ID: <1168885254.574206@bubbleator.drizzle.com>

Marten Lehmann wrote:

>> The data changed by a session in Oracle can never been seen by another
>> session until it is committed.  Why doesn't the session making the
>> change perform the verification test to begin with?

>
> Because it are two different applications. Currently, they are both
> written in Perl, but one of them is about to change to Java. So
> session-sharing is not possible.
>
> Our current process is easy: The first process that changes data is left
> open, the transaction is neither commited nor rolled back. Then I can
> perform tests on the data (and I know by design, that noone else is
> using the "dirty" data at the same time). If I'm happy with it, I commit
> the changes. If not, I will rollback them.
>
> 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.

> 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.

-- 
Daniel A. Morgan
University of Washington
damorgan_at_x.washington.edu
(replace x with u to respond)
Puget Sound Oracle Users Group
www.psoug.org

Received on Mon Jan 15 2007 - 12:20:55 CST