<literal>node2</literal>'s server to the required
        new version, e.g.:
<programlisting>
pg_upgrade
        --old-datadir "/opt/PostgreSQL/postgres/17/data2"
        --new-datadir "/opt/PostgreSQL/postgres/18/data2_upgraded"
        --old-bindir "/opt/PostgreSQL/postgres/17/bin"
        --new-bindir "/opt/PostgreSQL/postgres/18/bin"
</programlisting>
       </para>
      </step>

      <step>
       <para>
        Start the upgraded server in <literal>node2</literal>, e.g.:
<programlisting>
pg_ctl -D /opt/PostgreSQL/data2_upgraded start -l logfile
</programlisting>
       </para>
      </step>

      <step>
       <para>
        Enable all the subscriptions on <literal>node1</literal> that are
        subscribing the changes from <literal>node2</literal> by using
        <link linkend="sql-altersubscription-params-enable"><command>ALTER SUBSCRIPTION ... ENABLE</command></link>,
        e.g.:
<programlisting>
/* node1 # */ ALTER SUBSCRIPTION sub1_node2_node1 ENABLE;
</programlisting>
       </para>
      </step>

      <step>
       <para>
        On <literal>node2</literal>, create any tables that were created in
        the upgraded <literal>node1</literal> between <xref linkend="circular-cluster-disable-sub-node1"/>
        and now, e.g.:
<programlisting>
/* node2 # */ CREATE TABLE distributors (did integer PRIMARY KEY, name varchar(40));
</programlisting>
       </para>
      </step>

      <step>
       <para>
        Refresh the <literal>node2</literal> subscription's publications to
        copy initial table data from <literal>node1</literal> using
        <link linkend="sql-altersubscription-params-refresh-publication"><command>ALTER SUBSCRIPTION ... REFRESH PUBLICATION</command></link>,
        e.g.:
<programlisting>
/* node2 # */ ALTER SUBSCRIPTION sub1_node1_node2 REFRESH PUBLICATION;
</programlisting>
       </para>
      </step>
     </procedure>
    </sect3>

   </sect2>
 </sect1>

 <sect1 id="logical-replication-quick-setup">
  <title>Quick Setup</title>

  <para>
   First set the configuration options in <filename>postgresql.conf</filename>:
<programlisting>
wal_level = logical
</programlisting>
   The other required settings have default values that are sufficient for a
   basic setup.
  </para>

  <para>
   <filename>pg_hba.conf</filename> needs to be adjusted to allow replication
   (the values here depend on your actual network configuration and user you
   want to use for connecting):
<programlisting>
host     all     repuser     0.0.0.0/0     md5
</programlisting>
  </para>

  <para>
   Then on the publisher database:
<programlisting>
CREATE PUBLICATION mypub FOR TABLE users, departments;
</programlisting>
  </para>

  <para>
   And on the subscriber database:
<programlisting>
CREATE SUBSCRIPTION mysub CONNECTION 'dbname=foo host=bar user=repuser' PUBLICATION mypub;
</programlisting>
  </para>

  <para>
   The above will start the replication process, which synchronizes the
   initial table contents of the tables <literal>users</literal> and
   <literal>departments</literal> and then starts replicating
   incremental changes to those tables.
  </para>
 </sect1>
</chapter>