> Actually, I was connected to the database from an EMS IB Manager
> client while trying to execute this. When I closed the IB Manager
> client and tried it again, it worked.
>
> So, if you have a jdbc connection pool, and try to create the foreign
> key from a jdbc connection, does this mean it will fail if there are
> other open jdbc connections? Is there any workaround or planned
> further fixes for this?
>
> Thanks for the help...

It's not a failure - it's a protection device. You can't change metadata
while active transactions are ongoing. It's not regarded as good practice at
all to rifle your metadata while people are active.
Alan