Re: primary/ foreign key constraints for oltp, overhead?...soluti

Jared has a point. Is there an index on the foreign key?

Another minor detail: You should of course never update a primary key column, of course :-)

Amar Kumar Padhi wrote:

> Jared,
> I tried again and got the same result.
> on oracle 8.1.7 (RBO).
>
> session1 : delete from emp where deptno = 10;
>
> session2 : delete from dept where deptno = 30;
> session 2 hanged and waited till transaction in session one was committed.
>
> the max_trans on both tab is set to 255, incase this raises doubt.
> are you getting a different result? Is the FK present on the detail table
> you are trying with?
>
> rgds
> amar
>
> -----Original Message-----
> Sent: Monday, June 11, 2001 10:25 AM
> To: Multiple recipients of list ORACLE-L
> overhead?...soluti
>
> On Sunday 10 June 2001 21:50, Amar Kumar Padhi wrote:
> > - locks
> > Oracle generates internal locks on dict tables to maintain the data
> > integrity.
> > e.g.: I deleted a record from detail table in one session. In another
> > session I tried to delete a master record not related to the deleted
> detail
> > record. The 2nd session hanged. There were row-exclusive locks present on
> > the detail table and an exclusive lock present on an internal table (I
> > couldn't access). The same is the case with update.
> >
> > Oracle locks both the master & detail table records when the master record
> > is deleted and the foreign key is created with on delete cascade option.
> >
> > Bottomline, Oracle doesn't allow altering of master table primary key when
> > active transactions exists on detail table. Oracle will allow update of
> > columns other than the primary key.
>
> You should probably test this scenario, as it works fine for me.
>
> Delete the a child detail row.
> Delete an unrelated parent row, with delete cascade on the child table.
>
> Works fine.
>
> Possibly are missing an index? Some of these rules have changed I know,
> but I'll let you look up the details.
>
> Bottom line, it does work.
>
> Jared
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--
Venlig hilsen

Mogens Nørgaard

Technical Director
Miracle A/S, Denmark
Web: http://MiracleAS.dk
Mobile: +45 2527 7100


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