doc: clarify that pg_global can _only_ be used for system tabs.

Reported-by: zhoushulin1992@gmail.com
Discussion: https://postgr.es/m/160499688847.25495.8682880307938679648@wrigleys.postgresql.org

Backpatch-through: master

diff --git a/doc/src/sgml/manage-ag.sgml b/doc/src/sgml/manage-ag.sgml
index f9fe47b6a29d7c7cbfa3fbc63e9627d2693fbc19..a8a70a1fc4242eba3ce376c3b691e366af5a3969 100644 (file)
--- a/doc/src/sgml/manage-ag.sgml
+++ b/doc/src/sgml/manage-ag.sgml
@@ -504,7 +504,7 @@ CREATE TABLE foo(i int);
   <para>
    Two tablespaces are automatically created when the database cluster
    is initialized.  The
-   <literal>pg_global</literal> tablespace is used for shared system catalogs. The
+   <literal>pg_global</literal> tablespace is used only for shared system catalogs. The
    <literal>pg_default</literal> tablespace is the default tablespace of the
    <literal>template1</literal> and <literal>template0</literal> databases (and, therefore,
    will be the default tablespace for other databases as well, unless