Re: JDBC transaction isolation

=?ISO-8859-1?Q?Arne_Vajh=F8j?= <>
Thu, 03 May 2012 22:34:17 -0400
On 5/3/2012 10:08 PM, Richard Maher wrote:

On May 4, 7:57 am, Arne Vajh?j<> wrote:

On 5/3/2012 6:23 PM, Richard Maher wrote:

"Arne Vajh?j"<> wrote in message

Almost all database have it at the SQL level:

Is anyone else of the opinion that Oracle really does not support the
serializable isolation level? (At least not in the way that SQL Server, Rdb,
and I'm sure others do) That is, it doesn't prevent inserts to the other
txn's result-set,touched-rows by locking but rather fudges some sort of
snapshot/consistent-view of old data. (And even then with restrictions)
Eg: - select count(*) from employees where dept_code=1;

Oracle use MVCC instead of locking.

And that may seem to be cheating, but I believe it meet
the formal isolation level definitions.

Depends where you get your definition of "formal isolation
definitions" I guess: -


Definitive: -

That is how SQLServer implements it.

The definitive definition is in the SQL standard.

It says that serilizable prevents:
* dirty reads
* non repeatable reads
* phantom reads

Oracle meet that as all reads will return data as they were
at the start of the transaction.


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