>This thread has really gotten off the EJB track. Part of the "problem" is
>that people need to talk about some real products and implementations since
>most of us are concerned more with what can be done using EJBs today than
>what could be done in a theoretically environment.
Here's my understanding of how Oracle 8.xxx works with the so called DB OCC:
Scenario:
TX1 updates A, then updates B
TX2 updates B, then updates A
ISOLATION LEVEL=READ COMMITTED (Oracle default)
Outcome:
Deadlock. TX1 or TX2 is aborted.
ISOLATION LEVEL=SERIALIZABLE
Outcome:
If TX1 updates B before TX2 updates it, TX1 commits, TX2 is allowed to
continue
If TX2 starts before TX1, updates B before TX1 updates it, TX2 wins, TX1
aborts.
If TX2 updates A before TX2 updates it, TX2 commits, TX1 is allowed to
continue.
If TX1 starts before TX2 and updates A before TX2 updates it, TX1 wins, TX2
aborts
The aborted transaction receives ORA-08177 error.
Regards,
Hamid
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