Event ID 1848 — Schema Operations

Applies To: Windows Server 2008

Schema operations include the following:

• Updating the schema cache
• Updating the schema index
• Implementing schema modifications
• Maintaining schema integrity

Event Details

Resolve

Remove one of the conflicting schema objects

Event IDs 1845, 1847 through 1854, and 1895 through 1897 indicate there is a conflict in one or more schema objects. There are several procedures that you can use to resolve this issue. Perform the following procedures on a domain member computer that has domain administrative tools installed. After each procedure, check Event Viewer to determine whether the issue condition continues to be logged.

1. Update the schema cache.
2. Start Active Directory replication.
3. Disable one of the conflicting schema classes or attributes.
4. Restore the Active Directory database from backup media.

To perform these procedures, you must have membership in Domain Admins, or you must have been delegated the appropriate authority.

Update the schema cache

To verify a successful update of the schema, you can enable diagnostic logging for the schema. When diagnostic logging is enabled, a schema update produces Event ID 1582 in the Directory Service log of the Event Viewer. To enable diagnostic logging for the schema, you must edit the registry.

To update the schema cache:

Caution: Incorrectly editing the registry might severely damage your system. Before making changes to the registry, you should back up any valued data.

1. Open Registry Editor. To open Registry Editor, click Start. In Start Search, type regedit, and then press ENTER. If the User Account Control dialog box appears, confirm that the action it displays is what you want, and then click Continue. If the User Account Control dialog box appears, confirm that the action it displays is what you want, and then click Continue.

2. In the registry location HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NTDS\Diagnostics, in the left pane, right-click 24 DS Schema, and then click Modify.

3. Type 1 or higher (up to 5) for Value data to enable diagnostic logging for the schema. The higher the value, the more information is reported to the Directory Service log. Click OK.

4. Create a new text file named SchemaUp in a folder location that is convenient for you to access.

5. Copy the following five lines of text, and then paste them as the contents of the SchemaUp.txt file.

   dn:

   changetype: modify

   add: schemaUpdateNow

   schemaUpdateNow: 1

   -

6. After you paste the text into the file, ensure that there are no line breaks (carriage returns) between each line of text. If there are, delete the empty lines. Ensure that you have a hyphen as the last line of text in the file.

7. Save the file.

8. Open a command prompt as an administrator. To open a command prompt as an administrator, click Start. In Start Search, type Command Prompt. At the top of the Start Menu, right-click Command Prompt, and then click Run as administrator. If the User Account Control dialog box appears, confirm that the action it displays is what you want, and then click Continue.

9. Type ldif -i -f SchemaUp.txt, and then press ENTER. If necessary, type the file path to the text file that you saved. For example, if you saved the file in the Documents folder of an account named Administrator, type ldifde -i -f "c:\users\administrator\documents\schemaUp.txt", and then press ENTER.

10. Open Event Viewer. To open Event Viewer, click Start. In Start Search, type eventvwr.msc, and then press ENTER.

11. Expand Applications and Services Logs, and then click Directory Service.

12. Look for Event ID 1582, which confirms that the schema cache was reloaded successfully. If you do not see this event, click Find and type 1582, and then click Find Now. Event ID 1582 confirms that the schema cache was updated.

13. Confirm that there are no Critical, Error, or Warning events related to the schema after the schema cache update. To locate events that are related to the schema, click Find, type DS Schema, and then click Find Next.

14. Continue to click Find Next, and review each event until you have verified there are no Critical, Error, or Warning events that occured after the schema cache update.

Note: When you confirm that the schema cache was updated, you can set the 24 DS Schema value to 0 if you no longer need diagnostic logging for schema events. You can use the Reg command to modify the 24 DS Schema registry value. For example, to set the value of 24 DS Schema to 0, at a command prompt, type the following command, and then press ENTER:

Reg Add HKLM\SYSTEM\CurrentControlSet\Services\NTDS\Diagnostics /v "24 DS Schema" /t REG_DWORD /d 0

The number after /d indicates the value, in this case, the logging level. For example, to set the logging level to 1, change /d 0 to /d 1 in the previous command.

To learn more about the Reg command syntax and options, at a command prompt, type Reg /?, and then press ENTER.

Start Active Directory replication

To start Active Directory replication:

1. Open a command prompt as an administrator. To open a command prompt as an administrator, click Start. In Start Search, type Command Prompt. At the top of the Start menu, right-click Command Prompt, and then click Run as administrator. If the User Account Control dialog box appears, confirm that the action it displays is what you want, and then click Continue.
2. At the command prompt, type **repadmin /syncall /user:**domain\user **/pw:**password, and then press ENTER. Substitute the appropriate domain name, user name, and password for domain, user, and password, respectively. The command output indicates whether synchronization started successfully.

To perform the following procedure, you must have membership in Domain Admins and Schema Admins, or you must have been delegated the appropriate authority. Perform all steps on the computer that is logging the event to be resolved.

Disable one of the conflicting schema classes or attributes

To disable a conflicting schema class or attribute:

1. Obtain the name of a conflicting schema object from the event text in Event Viewer.
2. Open ADSI Edit. To open ADSI Edit, click Start. In Start Search, type ADSIEdit.msc, and then press ENTER. If the User Account Control dialog box appears, confirm that the action it displays is what you want, and then click Continue.
3. Right-click ADSI Edit, and then click Connect to.
4. In Select a well known Naming Context, click Schema. The default action of the tool is to connect to the local domain. If you want to connect to another domain or server, you can do that under Computer in the Connection Settings dialog box. Click OK.
5. In the console tree, expand Schema.
6. Click the object name CN=Schema.
7. In the middle pane, a three-column list of schema attribute and class names, class identifiers, and distinguished names appears. In the Name column, right-click the class or attribute that is named in the Event Viewer event text, and then click Properties.
8. In the class or attribute properties box, on the Attribute Editor tab, click the isDefunct attribute, and then click Edit.
9. Click True, and then click OK twice.
10. Close ADSI Edit.

For more information about disabling schema classes and attributes, see Disabling Existing Classes and Attributes (https://go.microsoft.com/fwlink/?LinkId=96256).

Restore the Active Directory database from backup media

To restore the Active Directory database from backup media, you need the Directory Services Restore Mode password. If you do not know the Directory Services Restore Mode password, you can reset it by using the Ntdsutil tool and the steps in article 322672 in the Microsoft Knowledge Base (https://support.microsoft.com/kb/322672).

To restore the Active Directory database from backup media:

1. At a command prompt that you opened as administrator, type bcdedit /set safeboot dsrepair, and then press ENTER. This causes the domain controller to enter Directory Services Restore Mode.
2. Restart the domain controller.
3. At the Windows logon screen, click Switch User.
4. Click Other User.
5. Type .\administrator as the user name, type the Directory Services Restore Mode password for the server, and then press ENTER.
6. Open a command prompt. To open a command prompt, click Start. In Start Search, type cmd, and then press ENTER.
7. At the command prompt, type wbadmin get versions -backuptarget:targetDrive:, and then press ENTER. Substitute the location of the backup that you want to restore for targetDrive.
8. Identify the version of the backup that you want to restore. You must enter this version exactly in the next step.
9. Type **wbadmin start systemstaterecovery -version:**dateTime -backuptarget:targetDrive:-quiet, and then press ENTER. Substitute the version of the backup that you want to restore for dateTime and the volume that contains the backup for targetDrive.
10. Open a command prompt, type bcdedit /deletevalue safeboot, and then press ENTER. The causes the domain controller to start up normally.
11. After the recovery operation completes, restart the domain controller.

Note: There is no need to attempt an authoritative restore because the schema cannot be restored by using an authoritative restore.

Verify

To verify that the schema is in a consistent state, complete the following procedures:

1. Ensure that the domain controllers synchronize their directory data by starting Active Directory replication.
2. Enable diagnostic logging for the schema.
3. Update the schema cache.
4. Verify that the schema was updated successfully by using Event Viewer.

To perform these procedures, you must have membership in Domain Admins, or you must have been delegated the appropriate authority.

Start Active Directory replication

To start Active Directory replication:

1. Open a command prompt as an administrator. To open a command prompt as an administrator, click Start. In Start Search, type Command Prompt. At the top of the Start menu, right-click Command Prompt, and then click Run as administrator. If the User Account Control dialog box appears, confirm that the action it displays is what you want, and then click Continue.
2. Run the command **repadmin /syncall /user:**domain\user **/pw:**password. Substitute the appropriate domain name, user name, and password for domain, user, and password, respectively. The command output indicates whether synchronization started successfully.

Enable diagnostic logging for the schema

To verify a successful update of the schema, you can enable diagnostic logging for the schema. When you enable diagnostic logging, a schema update produces Event ID 1582 in the Directory Service log of Event Viewer. To enable diagnostic logging for the schema, you must edit the registry.

To enable diagnostic logging for the schema:

Caution: Incorrectly editing the registry might severely damage your system. Before making changes to the registry, you should back up any valued data.

1. Open Registry Editor. To open Registry Editor, click Start. In Start Search, type regedit, and then press ENTER. If the User Account Control dialog box appears, confirm that the action it displays is what you want, and then click Continue.
2. In the registry location HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NTDS\Diagnostics, in the left pane, right-click the 24 DS Schema value, and then click Modify.
3. Type 1 or higher (up to 5) for Value data to enable diagnostic logging for the schema. The higher the value, the more information is reported to the Directory Service log. Click OK.

Update the schema cache

To update the schema cache:

1. Create a file to force a schema cache update using Ldifde.exe. Create a new text file named SchemaUp (SchemaUp.txt, if you are viewing file extensions) in a folder location that is convenient for you to access.

2. Copy the following five lines of text and paste them as the contents of the SchemaUp.txt file.

   dn:

   changetype: modify

   add: schemaUpdateNow

   schemaUpdateNow: 1

   -

3. After you paste the text into the file, ensure that there are no line breaks (carriage returns) between each line of text. If there are, delete the empty lines. Ensure that you have a hyphen as the last line of text in the file.

4. Save the file.

5. Open a command prompt as an administrator. To open a command prompt as an administrator, click Start. In Start Search, type Command Prompt. At the top of the Start Menu, right-click Command Prompt, and then click Run as administrator. If the User Account Control dialog box appears, confirm that the action it displays is what you want, and then click Continue.

6. At the command prompt, type ldif -i -f SchemaUp.txt, and then press ENTER. If necessary, type the file path to the text file that you saved. For example, if you saved the file in the Documents folder of an account named Administrator, type ldifde -i -f "c:\users\administrator\documents\schemaUp.txt", and then press ENTER.

Verify that the schema cache was updated successfully by using Event Viewer

To verify that the schema cache was updated successfully by using Event Viewer:

1. Open Event Viewer. To open Event Viewer, click Start. In Start Search, type eventvwr.msc, and then press ENTER.
2. Expand Applications and Services Logs, and then click Directory Service.
3. Look for Event ID 1582, which confirms that the schema cache was reloaded successfully. If you do not see the event, click Find, type 1582, and then click Find Now. Event 1582 confirms that the schema cache was updated.
4. Confirm that there are no Critical, Error, or Warning events that are related to the schema that occurred after the schema cache update. To locate events that are related to the schema, click Find, type DS Schema, and then click Find Next.
5. Continue to click the Find Next button and review each event until you have verified that there are no Critical, Error, or Warning events that occurred after the schema cache update.

When you confirm that the schema cache was updated, you may no longer need diagnostic logging for schema events. To disable diagnostic logging for schema events, use the Reg command to set the 24 DS Schema value to 0. To set the value of 24 DS Schema to 0, at a command prompt, type the following command, and then press ENTER:

Reg Add HKLM\SYSTEM\CurrentControlSet\Services\NTDS\Diagnostics /v "24 DS Schema" /t REG_DWORD /d 0

The number after /d indicates the value, in this case, the logging level. For example, to set the logging level to 1, change /d 0 to /d 1 in the previous command.

To learn more about the Reg command syntax and options, at a command prompt, type Reg /?, and then press ENTER.

Related Management Information

Schema Operations

Active Directory