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OpsMgr – Max Concurrent API reached – OS MP bug

July 17, 2013

A short post about a bug that has been posted by Kevin Holman earlier this year but has not been fixed yet.
The Alert is generated by the Windows Server 2008 Max Concurrent API Monitor in the Windows Server 2008 Operating System management pack version 6.0.7026.0.
The bug does not show on every server, but where it does, just disable the monitor.

What is MaxConcurrent API?

MaxConcurrentApi is a registry key which specifies the maximum number of simultaneous, logon-related, application programming interface (API) calls that can be transmitted across a secure channel at any one time.

Location: HKLM\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters


  • domain joined workstations: 1. One call at a time on member workstations.
  • domain joined servers: 10 beginning with Windows Server 2012. 10 threads for member servers. (Prior to Windows Server 2012 default was 2.)
  • domain controllers: 10 beginning with Windows Server 2012.  10 threads for domain controllers. (Prior to Windows Server 2012 default was 1.)

API calls can be transmitted concurrently only on secure channels that are digitally signed or encrypted.

So how do I know if the bug applies to a server?

When you have an alert on this just open the health explorer and check the information displayed on the State Change events tab for the monitor. If you select the state change where it went critical check out the details to see if a secure channel Error occurred:


let’s make those red buttons green again!


From → System Center

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