Transaction Isolation level issues

j8055 Aug 19, 2002 7:20 PM

I'm running some tests with JBoss where I'm spawning two threads within a 'test client'. The first thread updates a complex object and the second thread which is started half a second later simply attempts to read the same object. What I'm testing for is that the read thread returns the updated values not the initial values.

I have changed the transaction isolation levels within the database (SQL2K) configuration each of the following: TRANSACTION_SERIALIZABLE, TRANSACTION_REPEATABLE_READ, TRANSACTION_READ_COMMITTED, TRANSACTION_READ_UNCOMMITTED

When I set to either TRANSACTION_READ_COMMITTED or TRANSACTION_READ_UNCOMMITTED, my test runs through successfully and the results returned by the read thread are the updated values in the object thus it is not allowing a 'dirty read'.

However, when I set it to either TRANSACTION_SERIALIZABLE or TRANSACTION_REPEATABLE_READ the "read" thread hangs and eventually times out.

Does anyone know why I'm getting this kind of behaviour?

1. Re: Transaction Isolation level issues

nborwankar Aug 22, 2002 5:25 PM (in response to j8055)

You don't say whether you commit the transaction on the first thread or not. And whether that makes a difference to the behavior you see
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2. Re: Transaction Isolation level issues

davidjencks Aug 22, 2002 6:22 PM (in response to j8055)

I suspect you are deadlocking in the db. I don't have any personal experience with that db but have heard of some apps using it that had to set the isolation level to read uncommitted to avoid deadlock. I think they make liberal use of table or page locks at higher isolation levels.
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