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From Stefan Guggisberg <stefan.guggisb...@gmail.com>
Subject Re: Problems with concurrent sessions
Date Fri, 08 Jul 2005 08:31:43 GMT
On 7/8/05, Marcel Reutegger <marcel.reutegger@gmx.net> wrote:
> Hi Nicolas,
> 
> Nicolas Belisle wrote:
> > What is the session isolation level [ref.
> > http://www.unix.org.ua/orelly/java-ent/ebeans/ch08_03.htm] by default ?
> 
> the default is read commited.
> 
> > Is it configurable ?
> 
> no, but you may use locks to further control isolation level.
> 
> a session in jackrabbit will see changes as soon as they are committed.
> you may however use locks to achieve a higher isolation level.
> successfully setting a lock on a node will give you repeatable read for
> that subtree. if you do that on the root node you get serializable
> isolation level.
> 
> > At least, Jackrabbit seems to prevent dirty reads
> > (determined from tests). Is there any documentation regarding isolation
> > level ? I think it is a very important topic...
> 
> Unfortunately there is currently no documentation on isolation levels,
> but this thread may be a good starting point to collect all relevant
> information and then put it into a nice xdoc or wiki page.

dominique roughly sketched the 3 layers (transient, local, shared) 
involved in jackrabbit's implementation of the 'read committed' isolation level 
in an earlier thread:
http://article.gmane.org/gmane.comp.apache.jackrabbit.devel/1223

cheers
stefan

> 
> > Example :
> > A : open session
> > A : read nodes "test" & "test2"
> > B : open session
> > A : delete nodes "test" & "test2"
> > B : save session //WHAT SHOULD HAPPEN ??
> > B : logout
> > A : read nodes "test" & "test2" //WHAT SHOULD HAPPEN ??
> > A : logout
> 
> I cannot quite follow you here. thread B seems to save a session without
> having made changes to it? that means 'B : save session' is basically no
> op. But I guess that's not what you want to know...
> 
> regards
>   marcel
>

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