Collectd errors or problems can be obtained from
/var/log/opennms/. Collectd should be set to DEBUG mode in
log4j2.xml which can be found in
But if OpenNMS monitors many nodes, the debug collectd log file will grow ridiculous fast and it’s not easy to find the logs you are searching for.
A good approach to handle this is, to separate the logs from the problematic node into a new log file.
In the wiki you can find a how to article: https://wiki.opennms.org/wiki/Separate-collectd-log
SNMP data collecting issues
Please check also the SNMP performance data troubleshoot guide.