This follows up on the discussion in
http://archives.postgresql.org/pgsql-hackers/2008-03/msg01033.php
- pg_ctl will refuse a smart shutdown during online backup.
- The postmaster will also refuse to shutdown in smart mode
in that case and log a message to that effect.
- In fast shutdown mode, the server will rename "backup_label"
after successfully shutting down and log the fact.
Yours,
Laurenz Albe
