Environment:
Hibernate3.0
SQLServer 2005,
SQLJDBC 2005

Statement:
Session sess=HiberanteUtil.getSession();
Transaction tx=sess.beginTransaction();
int id=1;
User user=sess.get(User.class,id,LockMode.UPGRADE);
user.set... //5th line
...

when I debugged the program,I found two running threads reach the 5th line same time,which means they both obtained the exclusive locks of the same record.Didn't the get() method obtain the exclusive lock?
furthermore,how to lock the hole db table.
any answer will be appreciated.

Hi,
>>> when I debugged the program,I found two running threads reach the 5th line same time,
A) which means they both obtained the exclusive locks of the same record ?
B) Didn't the get() method obtain the exclusive lock?

LockMode.UPGRADE obtains a database level lock, if that is supported.
Oracle and PostgreSQL support it. I don't know about other databases.

Further, in this scenario ( I simulated on Oracle, Kindly excuse! I don't have SQL server. )
Both the transactions obtain exclusive lock of the same record, but in turns.
NOT AT THE SAME TIME.
Here, one transaction waits for the exclusive lock to be released by the other.
Thus, we see two running threads at the same time.
This is valid and expected.

>>> how to lock the hole db table ?
Hibernate doesn't support table level locks.
We can obtain them using jdbc, if the underlying database supports them.

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Thank you!
>>Both the transactions obtain exclusive lock of the same record, but in >>turns.
>>NOT AT THE SAME TIME.
>>Here, one transaction waits for the exclusive lock to be released by the >>other.
the second thread can't obtain the exclusive lock until the first thread commit the transaction or rollback it.Do I misunderstand it?

further,
according to Hibernate API Document,
LockMode.UPGRADE is An upgrade lock. Objects loaded in this lock mode are materialized using an SQL select ... for update.

Hi,
>>> the second thread can't obtain the exclusive lock until the first thread commit the transaction or rollback it.Do I misunderstand it?
No. You are correct.
Two transactions cannot simultaneously hold an exclusive lock on a row.

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