Oracle EBS R12 log file locations – here’s the link to a nice blog on the subject – note R12.2 will have changed somewhat due to the new file system layout so this link is not accurate for R12.2 – but R12.0 and R12.1 should be applicable.
http://onlineappsdba.com/index.php/2007/12/25/oracle-r1212i-log-file-patch-clone-startupshutdown/