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+#############################
+Upgrading from 3.0.x to 3.1.x
+#############################
+
+Before performing an update you should take your site offline by
+replacing the index.php file with a static one.
+
+Step 1: Update your CodeIgniter files
+=====================================
+
+Replace all files and directories in your *system/* directory.
+
+.. note:: If you have any custom developed files in these directories,
+	please make copies of them first.
+
+Step 2: Change database connection handling
+===========================================
+
+"Loading" a database, whether by using the *config/autoload.php* settings
+or manually via calling ``$this->load->database()`` or the less-known
+``DB()`` function, will now throw a ``RuntimeException`` in case of a
+failure.
+
+In addition, being unable to set the configured character set is now also
+considered a connection failure.
+
+.. note:: This has been the case for most database drivers in the in the
+	past as well (i.e. all but the 'mysql', 'mysqli' and 'postgre'
+	drivers).
+
+What this means is that if you're unable to connect to a database, or
+have an erroneous character set configured, CodeIgniter will no longer
+fail silently, but will throw an exception instead.
+
+You may choose to explicitly catch it (and for that purpose you can't use
+*config/autoload.php* to load the :doc:`Database Class <../database/index>`)
+::
+
+	try
+	{
+		$this->load->database();
+	}
+	catch (RuntimeException $e)
+	{
+		// Handle the failure
+	}
+
+Or you may leave it to CodeIgniter's default exception handler, which would
+log the error message and display an error screen if you're running in
+development mode.
+
+Remove db_set_charset() calls
+-----------------------------
+
+With the above-mentioned changes, the purpose of the ``db_set_charset()``
+method would now only be to change the connection character set at runtime.
+That doesn't make sense and that's the reason why most database drivers
+don't support it at all.
+Thus, ``db_set_charset()`` is no longer necessary and is removed.
+
+Step 3: Check usage of doctype() HTML helper
+============================================
+
+The :doc:`HTML Helper <../helpers/html_helper>` function
+:php:func:`doctype()` used to default to 'xhtml1-strict' (XHTML 1.0 Strict)
+when no document type was specified. That default value is now changed to
+'html5', which obviously stands for the modern HTML 5 standard.
+
+Nothing should be really broken by this change, but if your application
+relies on the default value, you should double-check it and either
+explicitly set the desired format, or adapt your front-end to use proper
+HTML 5 formatting.
+\ No newline at end of file