Re: JDBC transaction isolation

Lew <>
Thu, 3 May 2012 18:32:31 -0700 (PDT)
Arne Vajh=F8j wrote:

Lew wrote:

Richard Maher wrote:

Arne Vajh=F8j wrote ...

Almost all database have it at the SQL level: and

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,=


Are you referring to their database product or some other product, such =

as Java?

and I'm sure others do) That is, it doesn't prevent inserts to the othe=


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;

They do support SERIALIZABLE isolation, and properly by all evidence:




"Use the ISOLATION LEVEL clause to specify how transactions containing d=


modifications are handled.

"The SERIALIZABLE setting specifies serializable transaction isolation m=

ode as defined in the

SQL standard. If a serializable transaction contains data manipulation l=

anguage (DML) that

attempts to update any resource that may have been updated in a transact=

ion uncommitted at

the start of the serializable transaction, then the DML statement fails.=


See also


There's nothing in the definition of SERIALIZABLE transactions that requ=

ires locking.


So whatever anyone else's opinion, or yours, the facts seem to be that O=

racle Database

properly supports SERIALIZABLE transaction isolation. Why do you ask for=

 opinion when

facts are in evidence?

They meet the definition for transaction isolation level serializable.


It is more questionable whether MVCC (and Oracle is actually not the
only database vendor using MVCC != meet what most people associate
with serializable.

What does that matter? The term "serializable transaction isolation" is a t=
erm of art, with a
specific definition. Whatever "most people" associate with it notwithstandi=
ng. It's an objective
term with testable criteria for compliance. Oracle meets the test.

People are not entitled to wrong opinions on the definitions of terms of ar=
t, or any opinions, as to their definition.

Well - I think should use the database definition and not the
English definition when it actually is a database.


But I will not be surprised when somebody ask questions about it.

Surprise at the question is one thing. A correct answer is another.

I'm not evincing surprise at the question, only pointing out that the answe=
r is not a matter of opinion.


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