The default path name and the APT_CONFIG_FILE
The default name of the configuration file is default.apt and it is located in the Configurations directory in the Server directory of your installation
You can give the configuration file a different name or location or both from their defaults. If you do, assign the new path and file name to the environment variable APT_CONFIG_FILE. If APT_CONFIG_FILE is defined, the parallel engine uses that configuration file rather than searching in the default locations. In a production environment, you can define multiple configurations and set APT_CONFIG_FILE to different path names depending on which configuration you want to use.
You can set APT_CONFIG_FILE on a project wide level from the InfoSphere® DataStage® Administrator (see Setting environment variables) or for individual jobs from the Job Properties dialog.