Fix ERROR_DS_DUP_SCHEMA_ID_GUID (0X000020BD) on Active Directory

You're Stuck, But This Is a Quick Fix

I get it—midnight, panicked email from a client, their schema update just failed with ERROR_DS_DUP_SCHEMA_ID_GUID (0X000020BD). Happened to me last month with a medical software rollout. The error means Active Directory found two schema objects with the same schemaIDGUID. Here's the fix, and it's not complicated.

Step 1: Find the Duplicate GUID

You'll need ADSI Edit. Don't mess around with PowerShell for this one—ADSI Edit gives you direct access and you won't miss anything.

1. Open ADSI Edit (from Server Manager Tools or run adsiedit.msc).
2. Right-click ADSI Edit in the left pane, choose Connect to.
3. In the Connection Settings dialog, set Select a well known Naming Context to Schema. Click OK.
4. Expand the Schema container. You'll see hundreds of CN=Schema,CN=Configuration,... entries.
5. Press Ctrl+F to open the Find dialog. In the Find field, enter the schemaIDGUID value from your error log. The exact GUID is usually in the event log or the error message itself. If not, search for the attribute or class name you were adding (e.g., myCustomAttribute).
6. Right-click the found object, choose Properties, and scroll to schemaIDGUID. Write down the GUID.
7. Now, use Ctrl+F again, but this time search for the GUID value (like f0e29c77-3c3a-4b... ). Any results besides the one you just saw are duplicates. If the GUID isn't searchable directly, search for the attribute name again and manually compare the schemaIDGUID values of similar-looking objects.

Step 2: Delete the Duplicate

Once you find the duplicate object, delete it. But be careful—don't delete the original object that your schema extension is trying to create. The duplicate is usually an orphaned object from a failed schema update or manual import.

1. Right-click the duplicate object in ADSI Edit.
2. Select Delete. Confirm the deletion.
3. If the delete fails with a permissions error, you need to be a member of Schema Admins. Run ADSI Edit as that user.

Step 3: Retry the Schema Update

Now go back to your original schema update command or tool (e.g., ldifde, adprep, or a management console). Run it again. In my client's case, the schema update completed in under two minutes after removing the duplicate.

Why This Works

Active Directory assigns a globally unique identifier (schemaIDGUID) to every attribute and class in the schema. When you try to update the schema (like adding a new attribute for a custom application), AD checks if that GUID already exists. If it does—even if the object is orphaned or partially created from a previous failed update—the update stops dead with error 0X000020BD. Deleting the duplicate tells AD the GUID is free again, and the update proceeds.

Less Common Variations of This Error

Sometimes the duplicate isn't in the Schema container itself, but in the Configuration partition. This happens when you're extending schema from a third-party tool that botches the GUID generation. Check CN=Schema,CN=Configuration,DC=yourdomain,DC=com. Also, I've seen this pop up when someone manually edits the schema using ntdsutil and accidentally reuses a GUID from a deleted attribute.

Another variation: the error might show a different error code like 0x20BD without the ERROR_DS_DUP_SCHEMA_ID_GUID string. The fix is identical—find and delete the duplicate.

Prevention: Don't Let This Happen Again

First, always test schema updates in a lab. I know, everyone says that, but I had a client skip it because they were in a hurry—cost them four hours of downtime.

Second, when you delete a schema object, don't rush. Use ADSI Edit to verify the schemaIDGUID is unique before creating a new one. If you're using third-party software to extend schema, check its logs for GUID conflicts before applying it to production.

Third, consider using schemaIDGUID conflicts as a red flag that someone's been messing with the schema manually. Run a weekly script to check for duplicates in the Schema partition. It's overkill for most shops, but if you're running lots of custom apps, it saves your bacon.