| When I run test again, TC uses the very same data just used in first run |
Yes. Each Data Loop operation works according to its properties. So, if the properties say "run from the 1st record to the 10th record", it will work within this scope every time. If you want the Data Loop operation to take the next record on every run, you need to modify the operation properties so that the operation takes the record you want. Alternatively, you can use additional test commands that will "skip" the records which you don't need. However, I wonder why you want to run tests only for one record each time? You can go through all the needed records in one test.
Wyland, as far as I can see, the task you are talking about can be performed with TestComplete, but perhaps something is not configured properly in your test. I'd suggest that you send a sample test project and your data files to our Support Team, so that the guys can analyze your tests and see what is going wrong. Also, attach the link to this forum thread to your message.