freezing data by <command>VACUUM</> is still needed for shrink

<literal>pg_clog</> and <literal>pg_multixact</>. For historical reasons,

wording "autovacuum to prevent wraparound" is preserved for forced

atuvacuum for shrink <literal>pg_clog</> and <literal>pg_multixact</>.

autovacuum for shrink <literal>pg_clog</> and <literal>pg_multixact</>.

</para>

<note>