We at Six 9s Customer Research often have a need to concatenate dat files from SSI Web 6.4.2 survey versions to reach our client's goals.
For example, we recently conducted a survey in Japanese, Korean, Simple Chinese, Traditional Chinese, German, as well as English. We needed to combine the dat files from each and then process the combined dat file using SSI Web Data Cleaner to create new dat files for each of the client's plants in Germany, UK, Massachusetts, Ohio, Michigan, and China. We then created findings reports for each of the plants.
We concatenated the original dat files using Notepad. We then added some null answers to selected respondents who were missing some questions in order to use Data Cleaner to create the plant dat files. After getting help from Sawtooth Software Support on how to update the header entries of these added answers, all went well.
While our experience here was with SSI Web 6.4.2 dat files, the approach may work with ci3 dat files.