Hi John,
> From: A mailing list for Enterprise JavaBeans development
> [mailto:[EMAIL PROTECTED]]On Behalf Of John Harby
> Thanks for responding Winston. I think the local interface addition in the
> current draft handles the networking issues. The remaining
> bottleneck is the database access. Repetitive db calls via ejbLoad and
ejbStore are
> a big hit.
> BEA has tried to address this with some of their own extensions such as
> specifying the database as exclusive so that it is assumed no other SQL
> aside from the container will hit the CMP tables. But this is not usually
> useful since most environments will have several applications
> accessing the db. What I was suggesting was taking this to a smaller
granularity and
> allowing an individual CMP DD to specify that the table for the CMP was
> exclusive (not the entire database).
If an Entity bean doesn't have exclusive access to the database, there can
be two scenarios:
a) the competing process is another server in the same cluster
b) the competing process is something that has nothing to do with EJB
It seems to me that when people use db-is-shared=true, it's predominantly
because of scenario a). And in that case, the other process will obviously
be competing for access to the same table since it is an identical Entity
bean.
Your suggestion would only be an improvement for b), which I think only
represents a minority, but it's just my opinion.
What do you think?
> Another idea might be when I deploy a CMP, the db could cache a
> configurable percentage of rows in-memory (like in the db_block_buffers in
> Oracle) along with caching the execution plan for the SQL statement (e.g.
in Oracle's
> shared_pool). Since I already have the connection in the pool,
> the access of a row could be expedited. Implementing this sort of thing
would probably
> require a DB vendor such as Oracle, Sybase or IBM.
Not necessarily, we can always implement extensions that are specific to
certain databases.
About this pre-caching of rows, when should it occur? When the EJB is
deployed? On the first access? I think the latter would make sense, and it
could be implemented by returning scrollable collections.
--
Cedric
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