If the node that you are trying to connect is on a solaris or any unix platforum, then try these trouble shooting measures. 1. First check to see whether the agent is running by typing the following
command
lsnrctl dbsnmp_status

if you get the following message
"The db subagent is not started"

then follow the following steps:
i) try to do the following
lsnrctl dbsnmp_start
lsnrctl dbsnmp_status

Even after this step you couldn't start the agent do
the below specified steps
a) Check to see the log messages under
$ORACLE_HOME/network/log/dbsn*.log

if the logs show NMS-00001

b) Go to the directory $ORACLE_HOME/network/admin and rename the

mv snmp_ro.ora snmp_ro.ora.old
mv snmp_rw.ora snmp_rw.ora.old

c) Go to $ORACLE_HOME/agent and rename

mkdir q
mv *.q ./q
mv services.ora ./q

d) Start the Intelligent agent
lsnrctl dbsnmp_start

e) Confirm that it has started
lsnrctl dbsnmp_status

and also do
ps -ef|grep dbsnmp

f) Once after you confirm that you have succesfully
started the Intelligent agent

rm $ORACLE_HOME/network/admin/snmp_ro.ora.old
rm $ORACLE_HOME/network/admin/snmp_rw.ora.old
rm $ORACLE_HOME/agent/q/*.*


Good luck
Sam