Oracle FAQ Your Portal to the Oracle Knowledge Grid

Home -> Community -> Usenet -> c.d.o.misc -> Re: changing the isolation level

Re: changing the isolation level

From: DA Morgan <>
Date: Sun, 04 Feb 2007 09:05:46 -0800
Message-ID: <>

Marten Lehmann wrote:

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

Name one!

Name one reason why someone in an independent session would need to see uncommited entries that might very well be rolled back or changed, yet again, before being committed.

There is a difference between a value and data. If it isn't committed it is a value. If it is committed it is data.

> 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!

I don't. But I also don't believe there is any rational business purpose served by seeing that which is valueless.

> 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.

And think why it is that this system would not be able to do precisely what you describe without a dirty read if it uses Oracle's architecture. Think as long as you wish and you won't come up with one.

>>> 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.

Or perhaps it is because in Sybase writes block reads and reads block writes which is not the case in Oracle.

Your point of view is not disimilar to someone used to old-style airplane controls decrying the lack of cables in fly-by-wire. The cables aren't there because they are unnecessary.

Daniel A. Morgan
University of Washington
(replace x with u to respond)
Puget Sound Oracle Users Group
Received on Sun Feb 04 2007 - 11:05:46 CST

Original text of this message