Updated logging reference and HOWTO.
diff --git a/Doc/howto/logging.rst b/Doc/howto/logging.rst
index 2c9514a..44b2f59 100644
--- a/Doc/howto/logging.rst
+++ b/Doc/howto/logging.rst
@@ -651,6 +651,22 @@
code approach, mainly separation of configuration and code and the ability of
noncoders to easily modify the logging properties.
+.. warning:: The :func:`fileConfig` function takes a default parameter,
+ ``disable_existing_loggers``, which defaults to ``True`` for reasons of
+ backward compatibility. This may or may not be what you want, since it
+ will cause any loggers existing before the :func:`fileConfig` call to
+ be disabled unless they (or an ancestor) are explicitly named in the
+ configuration. Please refer to the reference documentation for more
+ information, and specify ``False`` for this parameter if you wish.
+
+ The dictionary passed to :func:`dictConfig` can also specify a Boolean
+ value with key ``disable_existing_loggers``, which if not specified
+ explicitly in the dictionary also defaults to being interpreted as
+ ``True``. This leads to the logger-disabling behaviour described above,
+ which may not be what you want - in which case, provide the key
+ explicitly with a value of ``False``.
+
+
.. currentmodule:: logging
Note that the class names referenced in config files need to be either relative