When you develop a mapping, you define data object read properties that determine how data is read from a flat file. The Data Integration Service can process the columns of the flat file data object that is based on a control file.
When the Data Integration Service constructs the column metadata based on the control file, it applies the following criteria for processing data:
The Data Integration Service applies default values for the column properties that you do not specify for the flat file data object
The Data Integration Service applies the default run-time properties of the flat file data object when you do not specify the run-time column properties in the control file. When you have additional columns in the control file without a data type, precision, or scale, the Data Integration Service uses the default data type, precision, and scale.
The Data Integration Service processes data as NULL for columns that do not appear in the control file but are present in the flat file data object
When the column in the flat file data object does not exist in the control file, the Data Integration Service processes the data as NULL during data preview. During run time, the Data Integration Service cannot process the column as that column does not exist in the control file.
The Data Integration Service fails mapping when the source metadata mismatches with a control file
The Data Integration Service fails to process the data when the source metadata based on the control file does not match the input data. For example, the Data Integration Service fails the mapping when the source contains a data type in the control file that is not compatible with the data type in the source.