.. include:: /Includes.rst.txt


.. _run-the-database-analyzer:

=========================
Run the Database Analyzer
=========================

While in the previous step, tables and columns have been *changed or added* to
allow running the upgrade wizards smoothly. The next step gives you the
possibility to *remove* old and unneeded tables and columns from the database.

Use the "Maintenance section" and click "Analyze Database".

.. figure:: ../../Images/Important-Actions-Database-Analyzer.png
   :alt: The Database Analyzer before analyzing the database.
   :class: with-shadow


You will be able to execute queries to remove these tables and columns so that
your database corresponds to the structure required for the new TYPO3 version.

.. warning::

   Be careful if you have deliberately added columns and/or tables to your
   TYPO3 database for your own purposes! Those tables and columns are removed
   only if you mark them to be deleted of course, but please be careful that
   you don't delete them by mistake!

.. note::

   TYPO3 does not directly remove tables and fields, but first renames them
   with a prefix `zzz_deleted_*`. This allows checking whether the fields and
   tables really are not needed anymore or were accidentally marked as deleted
   by wrong configuration.

   When you are sure you aren't going to need them anymore, you can drop them
   via the wizard.

Select the upgrades you want and press "Execute":

.. figure:: ../../Images/Important-Actions-Database-Analyzer-Updates-Executed.png
   :class: with-shadow
   :alt: Database analyzer

   The Database Analyzer

When you then click "Compare current database with specification" again and you
only see the message

.. figure:: ../../Images/Important-Actions-Database-Analyzer-Database-Analyzed.png
   :class: with-shadow
   :alt: Database analyzer

   The Database Analyzer with no updates to do.

then all database updates have been applied.