Re: deadlocks between single update statements ?

<hasta_l3_at_hotmail.com> wrote in message news:1159000862.384129.73710_at_i3g2000cwc.googlegroups.com...
> Dear group,
>
> Assume a transaction A with a single update statement updating many
> rows of a table.
> Assume another transaction B also with a single update, concurrently
> updating the same rows, but perhaps in a different order.
>
> Can these single updates deadlock ?
>

        If the row updates are in exactly the same
        order, the second transaction will wait for
        the first transaction to commit or rollback.

        If the row updates are in a different order
        you will get a deadlock.

> How do you prevent this ?
>

1. Serialize the two updates
2. Program for deadlock detection so that you can rollback and retry.

> Thanks much.
>

-- 
Regards

Jonathan Lewis
http://www.oracle.com/technology/community/oracle_ace/ace1.html#lewis

The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html

Cost Based Oracle: Fundamentals
http://www.jlcomp.demon.co.uk/cbo_book/ind_book.html