What is the use of node in data stage ?

The degree of parallelism, resources being used, and others in data stage are all determined during the run time based entirely on the configuration provided in the APT CONFIGURATION FILE.
Data stage jobs determine which node to run the process on, where to store the temporary data, where to store the dataset data, based on the entries provided in the configuration file. There is a default configuration file available whenever the server is installed.
You can typically find it under the “<>IBMInformationServerServerConfigurations” folder with the name “default.apt”. Bear in mind that you will have to optimize these configurations for your server based on your resources.