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typo3/sysext/scheduler/Documentation/AppendixA/Index.rst

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+.. ==================================================
+.. FOR YOUR INFORMATION
+.. --------------------------------------------------
+.. -*- coding: utf-8 -*- with BOM.
+
+.. include:: ../Includes.txt
+
+
+
+.. _technical-background:
+
+Appendix A – Technical Background
+---------------------------------
+
+This section aims to give some more in-depth information about what
+happens behind the scene in the Scheduler.
+
+When a task is registered with the Scheduler, an instance of the task
+class is created and stored in a database record as a serialized
+object. The database record itself contains additional information
+about the registration, mostly about past and future executions. The
+theory is that all the information that is really proper to the task
+should be defined as member variables of the task class and is thus
+encapsulated inside the task object. The information which relates to
+executing a registered task is stored in the Scheduler's database
+table.
+
+That being said, a task also contains information about its execution.
+Indeed each task class has an instance of
+:code:`TYPO3\CMS\Scheduler\Execution` as a member variable, which contains
+information such as start and end date and is used to calculate the
+next execution date.
+
+When a task is running, its start time is stored into an array, which
+is serialized and stored in the corresponding database record. If
+several executions are running at the same time, the array will
+contain several timestamps. Thus the "serialized\_executions" field
+actually contains an array of integers and not serialized instances of
+:code:`TYPO3\CMS\Scheduler\Execution` objects.
+
+