Just this excerpt from
http://technet.oracle.com/doc/server.815/a67781/c23cnsis.htm
Oracle offers the read committed and serializable
isolation levels, as well as a read-only mode that is
not part
of SQL92. Read committed is the default and was the
only automatic isolation level provided before Oracle
Release 7.3. The read committed and serializable
isolation levels are discussed more fully in "How
Oracle
Manages Data Concurrency and Consistency".
--- Jay Walters <[EMAIL PROTECTED]> wrote:
> You are still confused Gina, if you go into SQL*Plus
> and type the following
>
> create table foo ( x varchar(32));
> set autocommit off;
> insert into foo values ('gina');
> select * from foo;
>
> you will see the value just inserted and you are in
> the middle of the
> transaction. Rollback will clean out the table...
>
> This has always been (V4-V8i) and will always be...
> otherwise how would
> after triggers work for example. There is a freaky
> option in Oracle they
> put in just to blow out the TPC-A benchmark,
> discrete transactions, that
> doesn't let you read changes during the transaction.
>
> Cheers
> Jay
>
> -----Original Message-----
> From: Gina Hagg [mailto:[EMAIL PROTECTED]]
> Sent: Friday, June 15, 2001 1:15 PM
> To: [EMAIL PROTECTED]
> Subject: RE: [JBoss-dev] No storeEntity before
> ejbFind<METHOD>
>
>
> Sorry, I have been out for a while.
> Just wanted to say that
> Read committed is the default and was the only
> automatic isolation level provided before Oracle
> Release 7.3.
> And Read committed is still the default which
> doesn't
> let anybody even within the transaction see the
> updated changes.
>
> However, you are right, they added Serializable
> after
> 7.3 which you have to set up as the isolation level,
> which allows you within a transaction see the
> changes
> you have made.
> And it is only in this mode that you can.
> Of course, SQLPlus is Oracle specific which by the
> way
> uses SQLNet and not some JDBC-ODBC driver, and has
> serializable settings.
>
> Oracle does advise Read Committed as isolation
> setting
> , therefore i have rarely seen companies use
> anything
> but that...
> Sorry, if i caused confusion..
>
> --- David Jencks <[EMAIL PROTECTED]> wrote:
> > Hi,
> >
> > Hey guys, think a minute. What transaction
> > isolation means is _other_
> > transactions can't see your work until you commit.
>
> > Of course _your_
> > transaction can see everything you've done. If
> > you're working with say the
> > oracle interactive interface and insert a record
> in
> > a table, if you query
> > the table you can see it right away, you don't
> have
> > to commit first.
> > _other_ people can't see it until you commit.
> This
> > has nothing to do with
> > xa or anything else.
> >
> > [although there is a related issue with "tightly
> > coupled" and "loosely
> > coupled" transaction branches in xa: loosely
> coupled
> > means different
> > branches of the same transaction can't see each
> > others work. This should
> > only arise when several transaction managers are
> > using the same global
> > transaction against the same resource, and the
> > XAResources can't agree that
> > they are using the same resource. Maybe this is
> > what you guys are thinking
> > of, but this should only be a potential problem
> with
> > distributed jboss]
> >
> > I'm pretty sure someone else complained about this
> a
> > couple of weeks ago,
> > although I can't find the reference - they were
> > modifying an entity, then
> > doing a finder method returning a collection
> > including the "just modified"
> > bean, except they weren't seeing the
> modifications.
> >
> > In my opinion, if this requirement was not present
> > in ejb 1.1, is was a
> > serious requirements bug, encouraging logically
> > inconsistent behaviour from
> > the container.
> >
> > Thanks, Bill.
> >
> > david jencks
> >
> > On 2001.06.14 15:49:34 -0400 marc fleury wrote:
> > > |I have been working with databases for a long
> > time,
> > > |and particularly with Oracle, I am not aware
> that
> > this
> > > |can happen, whether in transaction or not,
> before
> > > |commit, nobody can see the updated table period
> > in the
> > > |database..
> > >
> > > well that is my point precisely, it seems to
> imply
> > that the updates
> > > "before
> > > the commit" are seen by connections enrolled in
> > the SAME transaction
> > > THROUGH
> > > THE DATABASE.... and frankly I am a bit
> > skeptical as to the level of
> > > support for these features in the db or even if
> > they exist at all or are
> > > just "wishful features" (heck they don't even
> > support 2pc and xa
> > > right)...
> > >
> > > so this smells of "teen spirit" to me... by
> > requiring "inflight"
> > > visibility
> > > of the changed records they put a difficult
> > requirement on the db drivers
> > > and I don't see it working well.
> > >
> > > They could have just required lock steps, as in
> > first commit the changes
> > > (and the db can follow that semantic) and then
> > issue your findBy as just
> > > another query...
> > >
> > > I am no db expert (they are rare these days) but
> > it strikes me as a
> > > misguided requirement.
> > >
> > > Bill for example couldn't you get the same
> > functionality with the
> > > serialiazed commits? Is this functionality that
> > you couldn't get
> > > otherwise?
> > > you are the first one to require this feature
> (and
> > you are savvy enough
> > > to
> > > scratch your itch so that is cool but still I
> > wonder...)
> > >
> > > but the REAL question is "is it true that you
> > cannot see changed tables
> > > from
> > > a connection participating in the SAME
> transaction
> > that changed it in the
> > > first place?"
> > >
> > > regards
> > >
> > > marcf
> > >
> > > |
> > > |I don't know much about XA, it having its own
> set
> > of
> > > |rules though.
> > > |
> > >
> >
> |__________________________________________________
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>
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