VACUUM on database with open transaction returns error?

In one window connect with psql to the database 'test' and execute


     test=# begin transaction;

In another window as the postgrs user do


     bash-2.04$ vacuumdb -z -a
     Vacuuming www
     VACUUM
     Vacuuming template1
     NOTICE:  RegisterSharedInvalid: SI buffer overflow
     NOTICE:  InvalidateSharedInvalid: cache state reset
     VACUUM
     Vacuuming test
     VACUUM
     Vacuuming photo
     VACUUM

     bash-2.04$ vacuumdb -z -a
     Vacuuming www
     NOTICE:  RegisterSharedInvalid: SI buffer overflow
     NOTICE:  InvalidateSharedInvalid: cache state reset
     VACUUM
     Vacuuming template1
     VACUUM
     Vacuuming test
     VACUUM
     Vacuuming photo
     NOTICE:  RegisterSharedInvalid: SI buffer overflow
     NOTICE:  InvalidateSharedInvalid: cache state reset
     VACUUM

     bash-2.04$ vacuumdb -z -a
     Vacuuming www
     VACUUM
     Vacuuming template1
     VACUUM
     Vacuuming test
     VACUUM
     Vacuuming photo
     NOTICE:  RegisterSharedInvalid: SI buffer overflow
     NOTICE:  InvalidateSharedInvalid: cache state reset
     VACUUM

     bash-2.04$

Back in the first window do:


     test=# COMMIT ;
     NOTICE:  InvalidateSharedInvalid: cache state reset
     COMMIT

OK, what gives?

1. Should I worry about these messages at all?

2. Is it supported to VACUUM a database with open transactions?
    If not: what am I suppoed to do?

3. Why does the NOTICE move around like this?

4. Are there any problems with my transaction in the first window?


Now I'm worried.....


    --- Allan.


PostgreSQL 7.1.2-4PGDG on Linux 2.4.7 i686 SMP (glibc 2.2.2-10)