The 'Properties mapping' tab in a Data Join component is used to:

The 'Properties mapping' tab in a Data Join component is crucial for managing how data from different data sources is integrated. The correct answer highlights that this functionality is used to copy property values from the joined data source to the primary source component. This means that when you establish a Data Join, the properties being mapped enable you to transfer relevant data fields from one dataset to another, effectively enriching the primary dataset with additional information.

This process is essential for ensuring that the data you are working with has all the necessary details for analysis or decision-making. By defining which properties to copy, the Data Join component allows for seamless data integration, making it easier to derive insights from comprehensive datasets.

For the other options, they serve different purposes that do not align with the primary function of the Properties mapping tab. Setting values for non-joined records, successfully joined records, or providing default values are aspects of data processing, but they do not describe the primary role of copying data from one dataset to another, which is the core action facilitated by this component.