With this option unselected, all stages of the external application are run on the execution environment selected when launching the external application. This is the default.
Execute as master process is not recommended for use with memory or cpu intensive tasks as the third party application will be launched on the master system without consideration of how busy that system is, or what processing capabilities it has.
For grid setups: Whether or not the Execute as master process option is enabled, export, import and post-processing steps will be run on a grid node if a grid execution environment is selected when launching an external application. Thus the Working directory option must be set to Shared temp-dir either way. See Working directory for more information about the Working directory settings.