[TASK] Add description why and when TYPO3 updates should be performed

Resolves: #451
Releases: main, 13, 12

Documentation/Installation/Index.rst

@@ -16,6 +16,7 @@ Installation
     Install
     DeployTYPO3
     ApplicationContext
+    Updates/Index
 
 ..  card-grid::
     :columns: 1
@@ -35,6 +36,11 @@ Installation
         This is a step-by-step guide detailing how to install TYPO3 for local
         development using DDEV, Docker and Composer.
 
+    ..  card:: :ref:`TYPO3 Updates <getting-started-typo3-updates>`
+
+        Here we explain the cycle of TYPO3 updates, and show you why and when
+        a TYPO3 update is useful.
+
     ..  card:: :ref:`Deploying TYPO3 <DeployTYPO3>`
 
         After you have installed TYPO3 locally, learn how to move your result

Documentation/Installation/Updates/Index.rst

@@ -0,0 +1,179 @@
+..  include:: /Includes.rst.txt
+
+..  _getting-started-typo3-updates:
+
+=================
+Maintaining TYPO3
+=================
+
+..  contents::
+    :caption: Content on this page
+
+..  _when-and-why-updates:
+
+When and why should we perform TYPO3 updates?
+=============================================
+
+With the newest version of TYPO3 the TYPO3 core developers present you the best
+version of TYPO3 CMS currently available on the market. It has the newest security features and the
+most amount of useful features. That is why you should always want to have your
+TYPO3 instances on the newest version possible. Another advantage is that you get free security fixes.
+
+In TYPO3 however, we follow a specific cycle which usually takes 1.5 years long. Every
+1 and a half year a new TYPO3 version occurs. You can follow the cycle `here <https://typo3.org/cms/roadmap>`__.
+
+We explain the different parts in the `roadmap <https://typo3.org/cms/roadmap>`__ now.
+When you follow the roadmap you see dark red strokes. They represent the **sprint releases**.
+Sprint release is a version that starts for example with v13.0 and then the next sprint release follows with v13.1.
+After the last sprint release (v13.3) the **Long Term Support release (LTS release)** v13.4 follows.
+The aim of the sprint releases is to test the new code with the new features extensively, until the LTS-release is
+reached. Therefore, the reason for sprint releases is to make the new code with the new features as agile and stable
+as possible. The order is: sprint release (0), sprint release (1), sprint release (2), sprint release (3), LTS release (4).
+Sometimes more sprint releases are possible.
+
+The green area represents the **regular maintenance** state. The orange area is the time where the focus lays on fixing
+bugs - so it is the **bug fixing phase**. The light orange area corresponds to the **extended support**. This means, when
+you want to get further bugfixes you have to book an
+`extended support <https://typo3.com/services/extended-support-elts>`__ which usually costs money.
+
+In the following we look a bit deeper into the types of updates. Otherwise, when you feel safe with the concepts you
+can use the :ref:`Upgrade Guide <t3coreapi:upgrading>` as a general or later reference to perform updates.
+
+..  _getting-started-major-minor-patchlevel-updates:
+
+Major, minor and patch level updates
+====================================
+
+In TYPO3 you can update your TYPO3 version. There exist three different types
+of updates:
+
+#.  Major updates: from for example 12.4.23 to 13.0.0
+#.  Minor updates: from for example 13.0 to 13.1
+#.  Patch and bugfix level updates (often security updates): from for example 13.4.0 to 13.4.1
+
+
+..  _getting-started-major-typo3-updates:
+
+Major updates
+-------------
+
+In major updates you will definitely have breaking changes and incompatible API
+changes.
+A breaking change can cause your system to break. You need to find a replacement
+for any usage that was removed or changed. For example in version 13.0 was a
+breaking change :ref:`Breaking: #101266 - Remove RequireJS <changelog:breaking-101266-1688654482>`.
+That means, whenever and wherever you used `requireJsModules` you have to find
+an replacement when you would like to have a working JavaScript functionality.
+All files that you included with `requireJsModules` will not be loaded anymore.
+When you update your TYPO3 version you should be aware of those changelog entries
+which you can find in the :doc:`Changelog reference <changelog:Changelog-13#changelog-v13>`.
+When dealing with a major version updates you usually have to use the backend module called **Upgrade wizard**. This
+module will take care of database table changes that came along with the new TYPO3 version.
+In TYPO3, we can separate a TYPO3 update into three stages: the :ref:`pre-upgrade stage <t3coreapi:preupgradetasks>`,
+:ref:`actual update <t3coreapi:upgradecore>` and the :ref:`post-upgrade stage <t3coreapi:postupgradetasks>`.
+
+..  _getting-started-minor-typo3-updates:
+
+Minor updates
+-------------
+
+Minor changes - `11.*.2`: For example 11.5 has new functionalities compared to
+11.4. The version 11.5 is compatible with 11. So withing a version like major
+11 the steps do not lead to breaking changes. For example in version 13.3
+compared to version 13.2 a new
+:ref:`Feature: #101252 - Introduce ErrorHandler for 403 errors with redirect option <changelog:feature-101252-1715447531>`
+was introduced.
+When performing minor updates you often have to clear the cache, run the Upgrade wizard and to run a database compare.
+Usually minor and patch changes are also referred to as **non-breaking** changes.
+
+..  _getting-started-patchlevel-typo3-updates:
+
+Patchlevel updates
+------------------
+
+Patchlevel changes - `11.5.*`: The version 11.5.2 indicates a backwards-compatible bugfix or patch release.
+It can be for example a security update. Clear the cache and check if website is working as expected. For further
+information we refer to the :ref:`Patch/Bugfix update guide<t3coreapi:minor>`.
+
+..  _getting-started-extension-updates:
+
+Extension updates
+=================
+
+In a TYPO3 instance you have usually have third party extensions installed. When you update your TYPO3 version you
+have to update the third party extensions too. In the **TYPO3 Extension Repository (TER)** you can enter the name of
+that extension and get information about supported TYPO3 versions. You find the TER `here <https://extensions.typo3.org/>`__.
+You will recognize that some extension developers stopped developing their extension further. We recommend that you only
+use third party extensions that are still supported.
+
+Useful commands to simplify the updates of extensions can be found in the :ref:`Upgrade extensions guide <t3coreapi:upgradingextensions>`.
+
+..  _getting-started-cronjobs:
+
+Cron jobs
+=========
+
+You can use cron jobs to do tasks that occur repeated. The backend module called
+:ref:`TYPO3 Scheduler <typo3/cms-scheduler:start>` can be used to perform a cronjob that you defined previously.
+In your terminal you can type
+
+
+..  code-block:: shell
+    :caption: Create or open the crontab
+
+    crontab -e
+
+to create a new job on unix-like operating systems. In :ref:`Setting up the cron job <typo3/cms-scheduler:cron-job>` you can
+see how this works. Normally you have to define the time interval in which the job should be performed frequently. To
+test your pattern you can insert it `here <https://crontab.guru/>`__ and test if it performs like you expect. When you
+are not familiar with cron jobs we refer to https://en.wikipedia.org/wiki/Cron. With a cron job you can for example
+create a fal cleanup or a sys history cleanup.
+
+
+..  _getting-started-deprecations:
+
+Deprecations
+============
+
+In TYPO3, deprecations indicate that a specific functionality will be removed in the next TYPO3 version. For further
+information we refer to the :ref:`article about deprecation <t3coreapi:deprecation>`. For example the
+:ref:`deprecation: #105171 - INCLUDE_TYPOSCRIPT TypoScript syntax <changelog:deprecation-105171-1727785626>`- notice is
+a deprecation notice telling you that in TYPO3 v14 you can't use the TypoScript syntax :typoscript:`INCLUDE_TYPOSCRIPT`
+to include TypoScript files anymore.
+
+..  _getting-started-little-helpers:
+
+Little Helpers: Rector and Fractor
+==================================
+
+In general you can use extensions like `rector <https://github.com/sabbelasichon/typo3-rector/blob/main/README.md>`__
+or `fractor <https://github.com/andreaswolf/fractor>`__ to find and replace deprecations. To reach this you have to
+fill out a configuration file (in rector file :file:`rector.php`, in fractor file :file:`fractor.php`) that defines
+the scope in which you want to perform deprecation replacements. For both extension is valid, only the rules that
+exist can find the respective deprecation. Here is an overview about the
+`existing rector rules <https://github.com/sabbelasichon/typo3-rector/blob/main/docs/all_rectors_overview.md>`__.
+When a rule is missing you can't find the deprecation. Check `here <https://getrector.com/find-rule>`__ if your desired
+rector rule exists already. When you feel able to create your own rector or fractor rule and want to publish it to the
+TYPO3 community, everyone using these tools would be happy to profit from your effort.
+
+..  _getting-started-logfile-rotations:
+
+Log file rotations
+==================
+
+
+..  _getting-started-sys-log:
+
+Sys log
+=======
+
+We have to take care of sys_log errors.
+
+..  _getting-started-language-updates:
+
+Language updates
+================
+
+After a TYPO3 update you have to update your translations. We refer to the article
+:ref:`Update backend translations <t3coreapi:update_backend_translation>`. You have to update the language packs that
+you are using.