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

Windows Service Monitor - Invalid class


This article discusses the issue when you are get an Invalid class error in a Windows Service Monitor component.


Error will appear like this in APM logs:

An exception occurred during polling processes. Error:<br />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 into 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



Last modified
11:19, 15 Jun 2017