# Degraded Scanclass Performance - UaTcpClientAcknowledgeHandler? **URL:** \ **Category:** Ignition\ **Tags:** ignition79\ **Created:** [May 7, 2019, 9:46pm UTC](https://forum.inductiveautomation.com/t/degraded-scanclass-performance-uatcpclientacknowledgehandler/24770 "2019-05-07T21:46:14Z")\ **Posts on this page:** 1\ **Showing post:** 2
**Author:** ![bfuson](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/bfuson/32/4597_2.png) [@bfuson](https://forum.inductiveautomation.com/u/bfuson)\ **Post date:** [May 7, 2019, 9:48pm UTC](https://forum.inductiveautomation.com/t/degraded-scanclass-performance-uatcpclientacknowledgehandler/24770/2 "2019-05-07T21:48:00Z")
Possible similar issue: > [@High CPU Usage for Thread](http://forum.inductiveautomation.com/t/high-cpu-usage-for-thread/20191): > > Hey all, Can someone tell me what this thread is? It’s constantly using a very high amount of CPU, if I restart the server it calms down for a week or two and then starts doing it again. I’m guessing it’s something for the UA server? How do I go about figuring out why it’s using so much CPU resources? Thread [ua-netty-event-loop-0] id=153, (RUNNABLE) sun.misc.Unsafe.unpark(Native Method) java.util.concurrent.locks.LockSupport.unpark(LockSupport.java:141) java.util.concurrent.SynchronousQ… Previous thread covering these peculiar UA servers: > [@OPC-UA Server Connections and Tag Issues](http://forum.inductiveautomation.com/t/opc-ua-server-connections-and-tag-issues/22206/19): > > Disabling the OPC UA server connection does stop the warnings Strangely when re-enabling the connection all the tag values report correctly, but the Bad\_ServiceUnsupported messages resume and the values/timestamps no longer update after the initial read. The sequence of UaSubscriptionChangeListener logs: [D] Synchronizing subscriptions… [D] Creating/deleting items on subscription ‘Scanclass ‘Default[default]’’ [D] nodesToAdd.size()=0 [D] nodesToRemove.size()=0 [D] Setting MonitoringMode to R… --- _[View the full topic](https://forum.inductiveautomation.com/t/degraded-scanclass-performance-uatcpclientacknowledgehandler/24770)._