On Fri, 28 Jul 2000 11:34:13 +0100, Lahooti, Hamid
<[EMAIL PROTECTED]> wrote:
>>I might be missing something here, but that seems rather dumb, since it
>>makes it impossible for the app.server to cache Entity data. Why? Well,
>
>You might consider it dumb but are you saying serialising access to the
>shared domain objects (as done by WLS) is smart?
Yes, it is smart for some applications. If the likelihood of sharing
instances between tx's is low, there is no penalty for using pessimistic
lo^H^H concurrency control, and thus is a good idea.
> Does it help concurrency?
Yes, if you don't want two tx's to access the same entity, but want to
use caching for performance, then it helps.
>As for instance data caching, there is no such requirements in the EJB
>spec
No, but this is a valid implementation choice that is beneficial in many
cases. Why are you assuming that just because you don't like it, noone
likes it?
> and IMO for good reasons:
>1) Cached data is only good as long as it's up to date. Not likely in
>multi-VM or transitional systems with legacy apps updating the DB directly.
Agreed, although the multi-VM thing assumes that the VM's share data.
This is not a required implementation restriction of multi-VM
containers...
>2) The best place to cache instance data is probably the DBMS cache
Why?
>3) You can always buy an ODBMS plugin for the container
I'm using RDBMS's most of the time.
Hmm.. make that always..
>IMHO applications that rely on caching of Entity data should use RDBMS cache
>or add ODBMS plugin to the container or use a different technology
>altogether,
This may be very inefficient if the Entities are somewhat coarse-grained
and made up of data from many tables of data.
IMHO you are making assumptions that indeed are valid in certain cases,
but please don't impose them on *all* cases.
>rather than compromise on container managed pessimistic concurrency control.
Again, you are assuming that your view is the only correct one. I'm not
saying that PCC is "best", and I am not saying that OCC is "best". They
are both "best", depending on the situation. I am merely trying to
identify the various characteristics of choosing either. That is all,
and which also happens to be on the primary purposes of this list.
I would suggest that you try to get a wider perspective of these issues.
Narrowmindedness is more than often a restriction than help.
/Rickard
--
Rickard �berg
Email: [EMAIL PROTECTED]
http://www.telkel.com
http://www.jboss.org
http://www.dreambean.com
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