I believe that when I passed "NUL" as the Oracle sqlplus spool file name, that Oracle created the NUL.LST file.
However, I have not yet found any way to delete this file? Any suggestions?
M:>dir *.lst
Volume in drive M is D
Volume Serial Number is 904D-B54E
Directory of M:\DW_Extract\Prod
2014-04-03 15:59 622 NUL.LST