Which transaction isolation level can prevent lost updates?

Hello there,

I am working on a multi-tier project, using Oracle 8i. My data layer consists of container-managed entity java beans, which means that I don't have direct control over which SQL statements are being generated, hence I cannot force X-locks via dummy-updates, nor by invoking SELECT FOR UPDATE. What I can do is to set the isolation level for the transactions my entity beans will execute within. Which transaction isolation level is necessary to prevent lost updates:

trans 1: trans 2:
begin;

            begin;
select i;

            select i;
i = i + 1;

            i = i + 1;
update i;

            update i;
commit;

            commit;

I know isolation level SERIALIZABLE would circumvent lost updates for sure. But I once read that REPEATABLE READ avoids lost updates as well, yet I am not sure whether that's true...

Thank you!

Kind regards,
Arno Huetter Received on Mon Nov 25 2002 - 13:45:53 CST