Hello Kevin, Thanks for your response. Not so sure I can see a need in my circumstance, but at least it's not a "bad thing to do" :D - maybe I'll see some areas where this might come in handy ....
As to the divergent states, I am mostly concerned about the Cache and ensuring that changes in one pu are "seen" in the other pu if that entity is cached. Perhaps I'm being bull-headed here, but how can I synch the caches? Thanks again & Cheers, John > -----Ursprüngliche Nachricht----- > Von: Kevin Sutter [mailto:kwsut...@gmail.com] > Gesendet: Freitag, 18. Mai 2012 20:42 > An: users@openjpa.apache.org > Betreff: Re: pro & contra of using Multiple Persistence Units > > John, in this case, thanks for the push... :-) I had missed > your first request... > > Using multiple persistence units is a fine practice and we > recommend that approach to many customers. Even when dealing > with the same datasource, some applications (or facets of an > application) just require different configurations for > accessing the data. A very common example is with the use of > optimistic vs pessimistic lock managers. Some apps may be > read-only or read-mostly and the default optimistic lock > manager is more than sufficient. While, other apps may be > heavier on the write processing and they may require a > pessimistic lock manager. > > There are many other cases where the multiple configurations > make sense. > > Of course, many of these configuration items can be > controlled from within your application as well, but if it's > a global configuration setting why not just set it in one > place and not complicate your code? > > You mentioned a concern about "divergent states of data"... > This is really an aspect of your application, not the use of > multiple persistence units. > As long as you are using the proper locking mechanism and > isolation levels when interacting with the database, it > doesn't matter if you are using one or several PU definitions. > > Good luck, > Kevin > > On Fri, May 18, 2012 at 1:28 AM, Boblitz John > <john.bobl...@bertschi.com>wrote: > > > > > > > > -----Ursprüngliche Nachricht----- > > > Von: Boblitz John [mailto:john.bobl...@bertschi.com] > > > Gesendet: Montag, 14. Mai 2012 15:07 > > > An: 'users@openjpa.apache.org' > > > Betreff: pro & contra of using Multiple Persistence Units > > > > > > Good Afternoon, > > > > > > I have been looking around the interwebs but can't seem > to find any > > > discussions regarding the advantages / disadvantages of using > > > multiple persistence units in a Java SE environment to > connect to a > > > single data source. > > > > > > Does anyone know of a good link? > > > > > > Also, any info/recomendations from the community would be > great ... > > > > > > A bit of Background: > > > > > > I am currently working on an application which splits it's > > > functionality across several services, mainly based on > the function > > > of the data (basic code tables, product data, employee data, etc > > > ...) and / or an sub-application (Invoicing, etc ...). > > > > > > Each of the services will obviously need to access data > from other > > > services, and it is currently designed that each service has it's > > > own Persistence Unit. IOW, basic code tables are "managed" in > > > packaged service with it's own persistence > implementation/unit JAR. > > > > > > I am a bit concerned that the various PU's will end up with > > > divergent states of the data, unless they can somehow be > synchronized. > > > > > > So, what I'm looking for is any information to help me > decide how to > > > best configure the persistence unit(s). > > > > > > > > > Thanks & Best Regards > > > > > > > > >  > > > > > > John Boblitz > > > > > > ---- > > > > > > Who is General Failure, and why is he reading my hard disk? > > > > > > > > > > One time push of my previous post, in the hopes that it was simply > > overseen. I will not do so again. > > > > John >
