NNM Caching

NNM caching is not the same as DNS caching, but the topic is raised here so the reader will appreciate that two kinds of caching are at work.

NNM performs a great many repetitive operations on the same devices. To avoid potentially expensive lookups of information from other services, it caches this information to improve overall performance. This information is written to disk, and survives an ovstop, ovstart, or reboot sequence. The downside of this data persistence is that external network configuration changes can cause NNM to lose contact with those devices that changed. The solution is to issue an xnmsnmpconf - clearCache command to clear the SNMP configuration cache. This should be done when the names and IP addresses of SNMP-managed devices change and NNM does not track the change. It may be necessary to delete the offending device from all maps before clearing the SNMP configuration cache. When the NNM database is deleted in preparation for a “starting over” discovery, it is also prudent to clear the SNMP configuration cache.