The Pass Unmapped Data feature of Data Mappings allows unmapped fields of the incoming data to be emitted as part of the outgoing data. By using this feature, the structure of the unmapped data will be retained when the data is passed on to the outgoing data.
Using Data Mapping Demo XYZ as example where not all fields from Source Schema (Data Schema A) are mapped to the fields in the Target Schema (Data Schema B), and the Pass Unmapped Data is used, the structure of data from Data Schema A that was not mapped to any field in Data Schema B should be retained when the data is passed on to the outgoing data.
You can verify this from the Logs tab of the Data Mappers plugin as shown from the sample screenshot below:
Clicking the Quick View icon located beside the Data column will also allow you to view the log information of the data received from the incoming data (Figure 1) and the data relayed to the outgoing data (Figure 2).
Figure 1: Data Received
Figure 2: Data Relayed
As you can see from the Data Relayed screenshot above, the age field from Data Schema A that was not mapped to any field in Data Schema B was passed on to the outgoing data using the same data structure from the source schema.