Update OOM wording.

doc/src/sgml/runtime.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.388 2007/12/16 11:22:33 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.389 2007/12/16 11:24:25 momjian Exp $ -->
 
 <chapter Id="runtime">
  <title>Operating System Environment</title>
@@ -1259,8 +1259,9 @@ Out of Memory: Killed process 12345 (postgres).
     Although this setting will not prevent the OOM killer from
     invoking altogether, it will lower the chances significantly and
     will therefore lead to more robust system behavior.  (It might also
-    cause fork() to fail when the machine appears to have available
-    memory.) This is done by selecting strict overcommit mode via
+    cause fork() to fail when the machine appears to have available memory
+    because of other applications with careless memory allocation.) This
+    is done by selecting strict overcommit mode via
     <command>sysctl</command>:
 <programlisting>
 sysctl -w vm.overcommit_memory=2