Floyd Marinescu wrote:
> Hi everyone,
>
> I was stumped by the following post on TheServerSide:
> http://www.theserverside.com:8080/patterns/thread.jsp?thread_id=220#2665
>
> Gal suggests that most ejbServers will load multiple instances of an
> entity bean with the same primary key inorder to service multiple clients.
>
> Is this true? Which app. servers do this?
>
Yes, it's true. Actually, I've played a little bit with three AppServers, and
only Weblogic didn't do this (except when the servers are clustered, which should
be the most common config.).
Both Inprise AppServer and iPlanet 6 can have multiple instances of the same
logical Entity Bean, because they chose to use optimistic concurrency instead of
pessimistic concurrency. This gives them a better performance, and no deadlocks.
To me, the choice made by WL in this area is wrong, because it leads to
deadlocks, and because the behavior becomes different when you go from a single
box to a clustered environment.
JB.
>
> He also suggests that serializeable transactions on these beans won't
> really be serializeable, how is that possible? What does it matter what
> concurrency algorith is used, the spec says serializeable transactions must
> occur in a serial fashion, so thats all a developer should be concerned with
> right?
>
> dazed and confused,
>
> Floyd Marinescu
>
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