This monitor verifies the availability of the Schema Master FSMO using an LDAP (Lightweight Directory Access Protocol) request. It periodically binds to the Domain Controller to verify the availability using an LDAP query.
Possible causes include the following:
The domain controller needs resizing.
The domain controller is a bridgehead server, and it is compressing large amounts of data because a bulk load must be replicated inter-site.
One or more other domain controllers failed, and their load transferred to this domain controller because it is now the closest available domain controller.
An application is placing a heavy load on the domain controller. This is usually caused by inefficient, CPU-intensive operations such as non-indexed queries.
The domain controller is critically low on memory.
The domain controller is under a denial-of-service attack.
View the error description in the alert for additional information.
View the overall system performance of the machine to determine if it needs additional resources.
Add additional domain controllers to help load-balance the load.
Ensure that there are a sufficient number of DCs in the active AD sites.
Capacity Planning for Active Directory Domain Services