The pattern or prefix used to search for names is only that which is to the left of the cursor. In this way you can refine your search simply by moving the cursor.

For example; suppose you have one hundred data sets called 'SYS1.A234.RGG.*' and you plan to use one named 'SYS1.A234.RGG.DBD0223.L422.FEB0299.TERRA'. You could type 'SYS1.A234.RGG' and press the AUTOTYPE key. That might return 'SYS1.A234.RGG.DBD0211.X331.AUG0599.FIRMA'. You can refine the next value returned by typing a '2' over the first '1' in 'DB0211' and then pressing the AUTOTYPE key again. This will use the new pattern and get you closer to the desired value.