My listener.log is growing every day .
To truncate the file I did
cat /dev/null >listener.log

but after that for every 10 mins I am getting a entry like service update ...Is this normal .In the old logfile I do not see this words ...

02-AUG-2002 11:38:40 * service_update * SPRDDEV * 0
02-AUG-2002 11:38:40 * service_update * SPRDUAT * 0
02-AUG-2002 11:38:40 * service_update * CMSDEV * 0
02-AUG-2002 11:38:40 * service_update * CAPSUAT * 0
02-AUG-2002 11:38:40 * service_update * CMSUAT * 0
02-AUG-2002 11:45:26 * service_update * CAPSDEV * 0
02-AUG-2002 11:48:40 * service_update * SPRDDEV * 0
02-AUG-2002 11:48:40 * service_update * SPRDUAT * 0
02-AUG-2002 11:48:40 * service_update * CMSDEV * 0
02-AUG-2002 11:48:40 * service_update * CAPSUAT * 0
02-AUG-2002 11:48:40 * service_update * CMSUAT * 0
02-AUG-2002 11:55:27 * service_update * CAPSDEV * 0
02-AUG-2002 11:58:41 * service_update * CMSDEV * 0
02-AUG-2002 11:58:41 * service_update * CAPSUAT * 0
02-AUG-2002 11:58:41 * service_update * CMSUAT * 0
02-AUG-2002 11:58:41 * service_update * SPRDUAT * 0
02-AUG-2002 11:58:41 * service_update * SPRDDEV * 0