All OTRS configuration files are stored in the directory Kernel and in its subdirectories. There is no need to manually change any other file than Kernel/Config.pm, because the rest of the files will be changed when the system gets upgraded. Just copy the configuration parameters from the other files into Kernel/Config.pm and change them as per your needs. This file will never be touched during the upgrade process, so your manual settings are safe.

The file Kernel/Config/Defaults.pm contains the parameters of the central OTRS framework. It defines all basic system settings such as the mail configuration, database connection, default charset and standard language. The file Kernel/Config/Files/Ticket.pm contains all configuration parameters for the trouble ticket system.

In the directory Kernel/Config/Files there are some other files that are parsed when the OTRS login page is accessed. If additional applications like the FAQ or the File Manager are installed, the configuration files for those can also be found in the mentioned path.

If the OTRS web interface is accessed, all .xml files in the Kernel/Config/Files directory are parsed in alphabetical order, and the settings for the central framework and additional applications will be loaded. Afterwards, the settings in the two files Kernel/Config/Files/ZZZAAuto.pm and Kernel/Config/Files/ZZZAuto.pm will be evaluated. Both files are used by the graphical interface for system configuration and should never be changed manually. Lastly, the file Kernel/Config.pm that contains your individual settings and manually changed configuration parameters, will be parsed. Reading the configuration files in this order makes sure that your specific configuration settings are used by the system.