The external procedure function is the main entry point into the external procedure module, and is an attribute of the External Procedure transformation. The dispatch function calls the external procedure function for every input row. For External Procedure transformations, use the external procedure function for input and output from the external procedure module. The function can access the IN and IN-OUT port values for every input row, and can set the OUT and IN-OUT port values. The external procedure function contains all the input and output processing logic.