Indexed data files contain a file header that describes the format and organization of the file. When opening an indexed data file, the Data File Editor reads the header information and uses it to format the file in the editor.
Line sequential, fixed length sequential and fixed length relative files do not have file headers, and therefore the Data File Editor cannot determine the format and organization by reading the data file directly. To enable the Data File Editor to obtain the file information required to properly render a data file, you can create a profile (.pro) file containing that information. When you create a non-indexed data file, the Data File Editor prompts you to create a profile file. When you edit the same data file again, Data File Editor automatically loads the header information contained in the profile file created for that data file. By default, the profile file is created in the same directory as the data file, using the same file prefix as the data file, plus a .pro extension.
If you try to open a line sequential, fixed length sequential or fixed length relative file that has no profile file, the Data File Editor will prompt you for file header details.