Disable logging of every connect request:

listener.ora:
LOGGING_ = OFF

otherwise the listener will log every connect and fill up the listener.log

[oracle@Database trace]$ ls -la
total 30696
drwxr-xr-x 2 oracle oinstall 4096 Aug 24 20:19 .
drwxr-xr-x 14 oracle oinstall 4096 May 4 09:18 ..
-rw-r—– 1 oracle oinstall 31393482 Aug 25 17:28 listener.log