Active Directory replication error 8418: Schema mismatch error if security descriptor is too large

Applies to: Windows Server version 1909Windows Server version 1903Windows Server version 1809

Summary


This article describes the symptoms and cause of Active Directory replication error 8418: "The replication operation failed because of a schema mismatch between the servers involved." This article also provides general steps to fix the errror.

This problem may be caused by a true schema mismatch or by a specific issue in which the schema mismatch error occurs because of a large security descriptor (SD).

Symptoms


Active Directory replication fails, and you receive the following schema mismatch error messages:


Additionally, the following events are recorded on the destination domain controller:


The promotion of a new domain controller may also fail. DCpromo logs information to the Dcpromo.log file at c:\windows\debug. In the event of such a failure, the DCpromo log displays an error entry that resembles the following:


On the source domain controller, you may find logged events from Security Descriptor Propagator that resembles the following:

Cause


This problem occurs because the SD on the problem object has exceeded the maximum size of 65,535 bytes. This is an operating system limitation.

Resolution


To fix this problem, reduce the size of the security ACL on the affected object. The error event will list the problem object. You must examine the ACLs on the object to determine which of them can be removed. Frequently, tools or scripts add duplicate Access Control Entries (ACEs).

The size also takes into consideration all inherited permissions. Depending on the object, it may be appropriate to clear any selected inherited permissions and remove inherited permissions from the object.

More information


The SD that is written to a certain active object may be successful if it is written locally. However, even if it is successful, the SD can still exceed the system limitation of 65,535 bytes on a replicated instance of the object. Therefore, this error may first surface as a replication problem. This is true also because replication results are often monitored closely.

The error may also occur locally on the originating DC. This is especially true if the object has children because additional explicit ACEs on a child object may cause the total SD size to exceed 65,535 bytes. In these cases, you would also experience SDPROP event 1450.

For the article that discusses other scenarios in which error 8418 may happen, see Troubleshooting AD Replication error 8418: The replication operation failed because of a schema mismatch between the servers involved.