In the old Business Units situation, the system fields are created in the ODX. The ODX Server is focused on extracting only the raw data from the data sources.
In some cases you like to use the DW_SourceCode to in data selection rules combined with conditions to filter the Test and Production datasource, based on the environment variable. This is not possible when using the ODX Server, because the DW_SourceCode is created in the MDW instance.
Only option left (as far is I know). Add a extra data area/datawarehouse layer, map Test and Production datasources in the same table, in the next data area/datawarehouse layer, filter on DW_SourceCode.
