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Isolation level settings

Brian Nice
Ranch Hand

Joined: Nov 02, 2000
Posts: 195
On question #1 in the mock exam, what is meant by declarative isolation levels and how is that different from transaction demarcation? I thought the transaction levels provided the isolation levels.
Pradeep bhatt
Ranch Hand

Joined: Feb 27, 2002
Posts: 8927

Transaction isolation level control how concurrently executing transactions are isolated from concurrently executing transactions.

Brian Nice
Ranch Hand

Joined: Nov 02, 2000
Posts: 195
I am still unlcear on what is meant by declarative isolation levels?
Kathy Sierra
Cowgirl and Author

Joined: Oct 10, 2002
Posts: 1589
Howdy -- well, there IS no way to set declarative isolation levels in EJB 2.0 (or EJB 1.1 -- and I can't remember now, but I'm pretty sure that you *could* do it in EJB 1.0... and it turned out to be a disaster so they got rid of it). If you COULD do "declarative isolation levels" it would mean that you could use the DD to, say, set things to allow/control for non-repeatable reads, dirty reads, phantom reads...
So, there is NOTHING in the EJB 2.0 spec that addresses isolation levels, so if you see something on the exam about isolation, run in the opposite direction Isolation levels can be set only at the individual resource level, programmatically, or of course through administration of the database itself.
Consider Paul's rocket mass heater.
subject: Isolation level settings
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