Customizations to the prlogging.xml file must be manually ported after upgrade
As a result of the upgrade from the Apache Log4j 1 logging service to the Apache Log4j 2 logging service, the name of the logging configuration file has changed from prlogging.xml to prlog4j2.xml and the format of the file has changed considerably. If you customized your prlogging.xml file, port the customizations to the new prlog4j2.xml file. If you do not port the changes, the Pega® Platform uses the default prlog4j2.xml file and disregards your customized prlogging.xml file.
For more information about customizing your log files, see the Apache Log4j 2 documentation.