Doc update for pg_start_backup

Added a note to the docs that pg_start_backup can take a long time to
finish now that we spread out checkpoints:

*** doc/src/sgml/backup.sgml 1 Feb 2007 00:28:16 -0000 2.97
--- doc/src/sgml/backup.sgml 28 Jun 2007 11:44:20 -0000
***************
*** 672,678 ****
<para>
It does not matter which database within the cluster you connect
to to
issue this command. You can ignore the result returned by the
function;
! but if it reports an error, deal with that before proceeding.
</para>
</listitem>
<listitem>
--- 672,682 ----
<para>
It does not matter which database within the cluster you connect
to to
issue this command. You can ignore the result returned by the
function;
! but if it reports an error, deal with that before proceeding.
Note that
! pg_start_backup can take a long time to finish. It performs a
checkpoint,
! and if one is already running it has to wait for it to finish
first. You
! can adjust <varname>checkpoint_completion_target</varname> to
perform the
! checkpoints more aggressively.
</para>
</listitem>
<listitem>

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com