Re: [ebxmlms-develop] Transaction Isolation Level Configuration

[Jason v. Z. <ja...@ze...>]

On Tue, 2003-02-04 at 02:25, Patrick Yee wrote:
> Hi Jason,
> 
> We have committed your modifications. Thanks for your contribution.
> 
> By the way, we would like to have more understanding about Axion. 

A little background. I tried to get the hsqldb project to work in a more
open fashion and found that not working so I took the original hsql code
left by Thomas Mueller and start Axion. We subsequently rewrote the
whole thing from scratch because of problems with the hsql code. It was
started as an in-memory database and when disk storage was added later
on it was a bit of a hack to say the least. Axion has an incredible
number of tests and overall great test coverage. It will soon be the
pure Java db of choice. Axion will soon come to Apache, to our new DB
project. I just published the first version of the site 10 minutes ago:

http://db.apache.org

> You say
> that it does not support transaction isolation in the current version. 

Currently axion supports "snapshot isolation" transactions, an isolation
level slightly stronger than TRANSACTION_SERIALIZABLE.

We're looking into adding the strongest of transaction isolation but
what is currently in Axion would more than likely suffice for most
needs. Rodney Waldhoff is looking into it.

> So,
> will it support rollback mechanism? 

Yes, it does now we just don't do the phantom reads. Rodney tells me it
wouldn't be hard to implement. If he doesn't have time to do it I will
do it in a few weeks.

> You know, if Hermes is working with a
> database without commit/rollback capability, or having some deficiency in
> transaction, there might be some scenario that causes harmful data
> inconsistency. We may need to include some warning in the documentation or
> property file in order to make the user conscious about that. What do you
> think?

Definitely, a warning would be good. I made sure not to provide the
option of no transactions. I'll do a little more research and try to
make a suggestion as to the basic minimum requirements for safe
operation.

> Regards, -Patrick
> --
> Patrick Yee
> System Architect
> Center for E-Commerce Infrastructure Development (CECID)
> Dept. of Computer Science and Information Systems
> The University of Hong Kong
> Tel: (852) 22415674
> Fax: (852) 25474611
> 
> 
> ----- Original Message -----
> From: "Frankie Lam" <fr...@mi...>
> To: "Patrick Yee" <kc...@ce...>
> Sent: Tuesday, February 04, 2003 3:14 PM
> Subject: Fw: [ebxmlms-develop] Transaction Isolation Level Configuration
> 
> 
> >
> > ----- Original Message -----
> > From: "Jason van Zyl" <ja...@ze...>
> > To: <ebx...@li...>
> > Sent: Thursday, January 30, 2003 4:16 PM
> > Subject: [ebxmlms-develop] Transaction Isolation Level Configuration
> >
> >
> > > Hi,
> > >
> > > I have a tarball with modifications to hermes to allow the transaction
> > > isolation level to be configured by the user if desired:
> > >
> > > http://www.apache.org/~jvanzyl/xa-isolation-levels.tgz
> > >
> > > I have modifed:
> > >
> > > hk.hku.cecid.phoenix.message.handler.Constants
> > > hk.hku.cecid.phoenix.message.handler.DbConnectionPool
> > > hk.hku.cecid.phoenix.message.handler.DiagTool
> > > hk.hku.cecid.phoenix.message.handler.MessageServer
> > >
> > > and added:
> > >
> > > hk.hku.cecid.phoenix.message.handler.IsolationLevelSelector
> > >
> > > It simply allows users to do the following:
> > >
> > > <Driver>org.axiondb.jdbc.AxionDriver</Driver>
> > > <User>user</User>
> > > <Password>password</Password>
> > > <URL>jdbc:axiondb:hermes:/tmp/hermes/db</URL>
> > > <TransactionIsolationLevel>SERIALIZABLE</TransactionIsolationLevel>
> > >
> > > If a transaction isolation level is not specified at all or
> > > misconfigured then the current behavior is employed where the most
> > > rigorous isolation level is used.
> > >
> > > --
> > > jvz.
> > >
> > > Jason van Zyl
> > > ja...@ze...
> > > http://tambora.zenplex.org
> > >
> > > In short, man creates for himself a new religion of a rational
> > > and technical order to justify his work and to be justified in it.
> > >
> > >   -- Jacques Ellul, The Technological Society
> > >
> > >
> > >
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> > >
> >
> 
> 
> 
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-- 
jvz.

Jason van Zyl
ja...@ze...
http://tambora.zenplex.org

In short, man creates for himself a new religion of a rational
and technical order to justify his work and to be justified in it.
  
  -- Jacques Ellul, The Technological Society