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From Andrus Adamchik <and...@objectstyle.org>
Subject Re: Cayenne external transaction
Date Tue, 21 Feb 2012 09:35:35 GMT
Of course there are multiple sources of DB modification. The question is - do they all have
to be in the same transaction ;)

On Feb 21, 2012, at 12:33 PM, Durchholz, Joachim wrote:

> This just made me wonder...
> 
>> A common reason to use external tx is when you want atomic behavior
>> across multiple sources of DB modification (say Cayenne and raw JDBC)
>> or mixing Cayenne with other non-JDBC transactional resources (JMS
>> for instance). If you only modify the DB via Cayenne, then you don't
>> need external tx.
> 
> Just a heads-up: That is not the normal case in corporate processing; there are always
other sources of database updates: Nightly batch processing, manual intervention through interactive
SQL, or third-party software that's interacting with your storage. You'd have to thread it
all through the Java service, which isn't always feasible or even desirable.
> Besides, if you don't have multiple sources of DB modification, you usually don't need
a DB. Not an SQL-enabled one anyway.
> 
>> you check out a local copy of your objects, you modify them, and then
>> commit. Only the last step involves a transaction and Cayenne can
>> handle starting and ending it internally with no user involvement.
> 
> What happens if a record is written that was modified by some third party?
> Ideally, Cayenne would avoid writing the udpates and instead report back that the application
was trying to write stale data.
> 


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