This option enables you to restrict the size of the log file and archive the resulting files.
If you do not use this option, the log file can become as large as is necessary.
You are using a log file (see Option -G<logfile>).
If you use this option, once the log file reaches the defined size, it is renamed to
<logfile name>_a_<start date>_<start time>-<end date>_<end time>.