> What used to happen is that the tables would gradually get locked,
> piecemeal, as Slony-I got to each one.  You could run into deadlock
> problems right near the end, which is a real waste.  By locking them
> up front, any failures will take place before any data is copied, so
> this minimizes time wastage.

Which is exactly why pg_dump does the saem thing.

Chris