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Home > Success Center > Server & Application Monitor (SAM) > SAM 6.6 Administrator Guide > Troubleshooting SAM > Service reporting Invalid Class issue in SAM

Service reporting Invalid Class issue in SAM

Updated: 3-9-2017

You may receive an error of Invalid Class for SAM services. The issue could be due to a number of issues including the incorrect polling method or issues with the WMI repository. If the following information does not resolve the issue, review information in our Success Center.

Verify the polling type

Services can be polled using RPC or WMI monitors. Verify the correct service is running for polling by navigating to Edit Application > RPC or WMI. If the correct monitor is used for polling, you may need to troubleshoot the monitors.

Repair the WMI Repository

If the WMI monitor is used for polling and returning an error of Invalid Class, you need to repair the WMI repository. Use this KB article to resolve the issue: 


Vista and Windows 2008 have a built-in method for repairing the WMI repository.

  1. Open an Administrator command prompt and run: winmgmt /salvagerepository/
  2. You may need to resync the counters if you continue receiving the error. Re-sync the counters by opening a command prompt and typing: winmgmt /resyncperf
  3. You should also verify the performance counters are not disabled.

You may also need to switch the polling method from WMI to RPC, or vice versa, by editing the monitoring node.

WMI is an operating system component. If the previous steps do no work, you may need to contact Microsoft for further information: WMI Troubleshooting. Microsoft Developer Network.

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