The ATG platform configuration layers allow you to make configuration changes and preserve them locally, without modifying the base configuration. Layers contain the properties files previously described, and can be stacked up in a variety of ways to create different configurations for different purposes.
The configuration stack is defined by the Nucleus CONFIGPATH. The CONFIGPATH is determined from the MANIFEST.MF files for the ATG application modules included in the application (see the Working with Application Modules chapter of the ATG Programming Guide for module information). Nucleus locates configuration properties by examining the properties files in the directories and JAR files, in the order they appear in the CONFIGPATH. The result is a combination of property values found in each of the files or directories. If the same property value is defined in more than one properties file (layer), values found later in the configuration path override the values found earlier. The localconfig directory usually appears last in the CONFIGPATH, so that any properties defined there override default system settings.
For example, suppose you change the port number for ATG’s internal RMI server, by setting the rmiPort property of the /atg/dynamo/Configuration component, and save the new value in the localconfig directory. The next time you start the application, Nucleus will take the value of the rmiPort property from localconfig, because it is the last directory in your configuration path.
Any changes you make to the Local configuration layer are preserved when you install a new ATG version.
Note: The ATG Control Center shows the configuration layers used by the application to which you are currently connected. Depending on the complexity of your system, additional layers may exist within your ATG installation. For example, the ATG platform includes a liveconfig configuration layer that is disabled by default, which contains settings appropriate for deploying your applications in a production environment. For more information, see Enabling liveconfig Settings in the Configuring for Production chapter.
