<listitem>

<para>

Specifies a libpq connection string to connect to the source

<productname>PostgreSQL</productname> server to synchronize the target with.

The connection must be a normal (non-replication) connection

with superuser access. This option requires the source

server to be running and not in recovery mode.

<productname>PostgreSQL</productname> server to synchronize the target

with. The connection must be a normal (non-replication) connection

with a role having sufficient permissions to execute the functions

used by <application>pg_rewind</application> on the source server

(see Notes section for details) or a superuser role. This option

requires the source server to be running and not in recovery mode.

</para>

</listitem>

</varlistentry>

<refsect1>

<title>Notes</title>

<para>

When executing <application>pg_rewind</application> using an online

cluster as source, a role having sufficient permissions to execute the

functions used by <application>pg_rewind</application> on the source

cluster can be used instead of a superuser. Here is how to create such

a role, named <literal>rewind_user</literal> here:

<programlisting>

CREATE USER rewind_user LOGIN;

GRANT EXECUTE ON function pg_catalog.pg_ls_dir(text, boolean, boolean) TO rewind_user;

GRANT EXECUTE ON function pg_catalog.pg_stat_file(text, boolean) TO rewind_user;

GRANT EXECUTE ON function pg_catalog.pg_read_binary_file(text) TO rewind_user;

GRANT EXECUTE ON function pg_catalog.pg_read_binary_file(text, bigint, bigint, boolean) TO rewind_user;

</programlisting>

</para>

<para>

When executing <application>pg_rewind</application> using an online

cluster as source which has been recently promoted, it is necessary

to execute a <command>CHECKPOINT</command> after promotion so as its

control file reflects up-to-date timeline information, which is used by

<application>pg_rewind</application> to check if the target cluster

can be rewound using the designated source cluster.

</para>

<refsect2>

<title>How it works</title>