Hi Shaku,
You previously asked about a different observed error, “Qos 0 channel not writable”:
https://community.hivemq.com/t/qos-0-channel-not-writable/1499
For “Qos 0 memory exceeded” errors, everything @michael_w advised should still apply - it’s usually an issue of topic client subscriber consumption being a bottleneck. What was the outcome after reviewing his advice? Did you consider moving to a later version?
This is the Control Center analytics documentation for our current release if it could also be helpful:
https://www.hivemq.com/docs/hivemq/4.11/control-center/analytic.html#dropped-messages
Thanks,
Seth - HiveMQ Support