Thread: Re: [GENERAL] Database replication... - Mission Critica

> > This is wrong assumption. If
> >
> > 1st client executes UPDATE t SET a = 1 WHERE b = 2;
> > 2nd client executes UPDATE t SET a = 2 WHERE b = 2;
> >
> > at "the same time" you don't know in what order these
> > queries will be executed on two different servers (because
> > you can't control what transaction will lock record(s)
> > for update first).
>
> I guess we would need two phase commit in this case. Then it could be
> guaranteed.
>

I'm not sure 2PC would guarantee order here.  There is
potential for a dead lock across system boundary in this
example.  If the pre commit messages were sent at the same
time which server would lock the resource?


Darren