Actually, I believe that Ian has touched on something that separates many of us
in our design decisions. I always assume that the persistence layer is
accessed by applications outside of the EJB system. That's one of the reasons
that EJB is so nice, it helps manage transactional isolation. If your system
is only accessed by the EJB server, then you have more flexibility in your
design.
Ian McCallion wrote:
> Robert Krueger asked why Caching is a value-add of CMP and why BMP prevents
> you from caching.
>
> The answer is that BMP doesn't prevent you from caching if you have a
> single application doing all database updates via a single cache.
>
> However if the database is accessed both via the cache and via other
> mechanisms (eg there could be a Client-server SQL application also
> accessing the database, or there could be two systems sharing the database,
> each having its own cache) then CMP is necessary because the container
> needs to know if the data in the cache is current and this requires the
> container to know the relationship between cached objects and database
> records.
>
> With BMP this knowledge is buried in the application.
>
> Ian McCallion
> CICS Business Unit
> IBM Hursley
> [EMAIL PROTECTED]
> Tel: ++44-1962-818065
> Fax: ++44-1962-818069
>
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--
Richard Monson-Haefel
Senior Consultant
BORN Information Services
Author of Enterprise JavaBeans
Published by O'Reilly & Associates
(Available June 1999)
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