Document that increasing max_connections uses more resources.

Roberto Mello

Discussion: http://postgr.es/m/CAKz==bJBCWrvN77fmuZ2XqD3jazWEb=E80AA4Yv9C9tQ61YDdQ@mail.gmail.com

doc/src/sgml/config.sgml

@@ -707,6 +707,12 @@ include_dir 'conf.d'
         only be set at server start.
        </para>
 
+       <para>
+        PostgreSQL sizes certain resources based directly on the value of
+        <varname>max_connections</varname>. Increasing its value leads to
+        higher allocation of those resources, including shared memory.
+       </para>
+
        <para>
         When running a standby server, you must set this parameter to the
         same or higher value than on the primary server. Otherwise, queries