Re: changing the isolation level

Frank van Bortel wrote:
> Charles Hooper schreef:
> >
> > What you need is READ UNCOMMITTED ISOLATION LEVEL. See:
> > http://www.oracle.com/technology/oramag/oracle/05-nov/o65asktom.html
> > "The READ UNCOMMITTED isolation level allows dirty reads. Oracle
> > Database doesn't use dirty reads, nor does it even allow them."
> >
> > Charles Hooper
> > PC Support Specialist
> > K&M Machine-Fabricating, Inc.
> >
> Meaning: your application needs a major overhaul, and was
> written without the proper understanding of transaction.
>
> --
> Regards,
> Frank van Bortel
>
> Top-posting is one way to shut me up...

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?

Besides the referenced article you need to see the Concepts manual and read up on the read consistency model of Oracle.

From: Oracle9i Database Concepts Release 2 (9.2) Part Number A96524-01, Ch 1, Introduction to the Oracle Server
>>

Read consistency, as supported by Oracle, does the following:

Guarantees that the set of data seen by a statement is consistent with respect to a single point in time and does not change during statement execution (statement-level read consistency)

Ensures that readers of database data do not wait for writers or other readers of the same data

Ensures that writers of database data do not wait for readers of the same data

Ensures that writers only wait for other writers if they attempt to update identical rows in concurrent transactions

The simplest way to think of Oracle's implementation of read consistency is to imagine each user operating a private copy of the database, hence the multiversion consistency model. <<

HTH -- Mark D Powell -- Received on Sun Jan 14 2007 - 11:20:33 CST