You can use a JSON file to Using the Positional layout, you can define the structure of your Fixed Length file either at Source or Destination layout. You need to specify the names and the positions of required fields in order to identify these fields.
To create a JSON file Positional layout:
- Select JSON from Positional from the Source data format drop-down list.
- Click
to create a JSON layout from the source data layout.
- On the Create Layout window, provide the name of the JSON Positional layout.
- Click Next to upload a sample JSON Positional file.
Click Browse to upload a sample JSON Positional file that you want to use for defining the Source or Destination structure.
.Drag the column edge to re-size the width of each column as per the required character length.
Info If you need column headers, click the default column names to change them manually. In addition, the column width is also not automatically adjusted as per the uploaded sample file. You need to re-size the width of each column manually. 
- You may click each column to modify the default names in the Column field.
- Click the column header of the required column to edit, insert, split, or delete it.
- Select Column Attribute to choose the data type for each column.
Choose the type, alignment, and description for values of each column.
Click Save to save the JSON selected column attribute.
Click Save to save the Positional layout.