Ubuntu 16.04 System Monitoring

Problem:
Unable to graph the values of ucd-memory (MIB Group) on my Linux Ubuntu 16.04 using Data Collection Group File ‘netsnmp.xml’.

I am not sure if I missed anything on Opennms. However, ONMS is able to graph other MIB Groups (shown below).

Please help me.

Expected outcome:
Graph on ‘Resource Graph’ function the below values and make some custom alarms & notifications:
.1.3.6.1.4.1.2021.4.3 memTotalSwap
.1.3.6.1.4.1.2021.4.4 memAvailSwap
.1.3.6.1.4.1.2021.4.5 memTotalReal
.1.3.6.1.4.1.2021.4.6 memAvailReal
.1.3.6.1.4.1.2021.4.11 memTotalFree
1.3.6.1.4.1.2021.4.13 memShared
1.3.6.1.4.1.2021.4.14 memBuffer
1.3.6.1.4.1.2021.4.15 memCached
1.3.6.1.4.1.2021.4.100 memSwapError

OpenNMS version:
Version: 23.0.0