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Home > Success Center > Server & Application Monitor (SAM) > SAM - Knowledgebase Articles > Windows Service Monitor - Invalid class

Windows Service Monitor - Invalid class


When you are getting an Invalid class error in a Windows Service Monitor component, review the polling method used to poll the node and your settings for Disable Performance Counters in the registry.


In the APM logs, you will find the following error message:

An exception occurred during polling processes. Error: Invalid class


All versions of SAM


Scenario #1
This problem is caused by a WMI issue on a monitored node and can be fixed by changing the polling method from WMI to RPC


Scenario #2

"Disable Performance Counters" in registry is enabled (set to '1')


Scenario #1

  1. Edit the application monitor.
  2. Select all Windows Service Monitor components.
  3. Click on Multi Edit.
  4. Set Fetching Method to RPC.
  5. Save the settings.


Scenario #2

  1. Log in to the affected server.
  2. Start > Run > regedit
  3. Locate "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\PerfProc\Performance".
  4. Locate "Disable Performance Counters", and confirm if its value is 0.
  5. If it is 1, modify the key, and change it from 1 to 0.
  6. Stop and start "Windows Management Instrument" service via services.msc.



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