Added system variable @CFDT = 900(number of seconds per 100K), if cache file is older than @CFDT, then delete it and re-get data from web.
Remember URL-to-File mapping across sessions. the cache file can be used by multiple Origin applications, then do not need to re-download if the file is not older than @CFDT.
Add LT cmd to delete URL-to-File mapping cache, for example:
delete -web "http://www.sidc.be/silso/INFO/snmtotcsv.php";