Stat/Transfer always writes a log that is displayed in the Log dialog box. You can view it and, if you would like, manually save it to disk. However, the options described here control a different feature that will automatically write a log file to disk every time you do a data transfer.
Always write a log file
To turn on this feature, check the option Always write a log file.
By default the log file will have the same path and name as the output file, but will have the extension .stlog. You can change this behavior by entering a different value in the Filename field. You can use the following macros:
%ipath% The path, including the drive (on Windows), of the input data file
%iname% The name, without the extension, of the input data file
%opath% The path, including the drive (on Windows), of the output data file
%oname% The name, without the extension, of the output data file
If log file exists
This option controls what happens if the log file exists in the location that you have specified. The possible values are:
Prompt before overwriting
Overwrite without asking
Append to existing log
The last option, "Append to existing log", is the default.