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Hibernate version: 3.0

1. What are the types of transaction management within hibernate. Is each hibernate transaction always executed within context of active database transaction. Does maybe exist sth like optimistic concurrency control.s
2. What transactions isolation levels is it possible to set?

HIbernate will use the underlying transaction manager that you have configured. Isolation levels are JDBC/Database determined - again outside of hibernate so it will just use it as you have configured it.

So anything is done within hibernate transaction is done within active SQL transaction? Begin and commit(rollback) of hibernate transacion exacly refer to begin and commit of SQL transaction in the underlying database. (or maybe SQL transaction is begun atfter hibernate transaction is committed to update all changes that were made to persistent objects?)
thx for explanations once again...