Re: serializable isolation level behavior question

<harvinder76_at_gmail.com> wrote in message news:1161031234.430942.187950_at_m7g2000cwm.googlegroups.com...
> Hi,
>
> We are testing concurrency performance and trying to isolate the issue
> using sqlplus and some dummy tables and need some clarification.
> Following is the scenario:
>
> Session 1 (isolation level read committed)
>
> Insert into dd values(1);
> Commit;
> Insert into dd values(2);
> Commit;
>
>
> Session 2 (isolation level serializable)
>
>
> Set transaction isolation level serializable
>
> Select * from dd; (2 rows returned at this point)
>
> Now issue another insert from session 1
> Insert into dd values(3);
> Commit;
>
> Now run the select again from session2:
> Select * from dd; (still return 2 rows)
>
> Now truncate the table from session1:
> Truncate table dd; (issue implicit commit)
>
> Now again run the following select from session 2:
>
> Select * from dd; (This should still shows 2 rows as
> read data from rollback segments since in serializable mode, it need to
> show the pre-image before the truncate but it is showing 0 rows)
>
> Is this expected behavior that in second session it returns 0 rows and
> not 2 rows?
>
> Thanks
> --Harvinder
>

Yes, truncate does not generate any undo. In this case, you should use delete instead. Received on Mon Oct 16 2006 - 18:39:58 CDT