XADM: The ADC Does Not Work in an Environment That Contains More Than 800 Domain Controllers (314950)

IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows Registry

SYMPTOMS

In a Microsoft Windows 2000 forest that contains more than 800 domain controllers, the Active Directory Connector (ADC) Connection Agreements may not run and an error message that is similar to the following may be logged:

Event Type: Error
Event Source: MSADC
Event Category: LDAP Operations
Event ID: 8270
Date: 12/3/2001
Time: 4:33:51 AM
User: N/A
Computer: PARSIFAL
Description:
LDAP returned the error [b] Administration Limit Exceeded when importing the transaction dn: CN=Connection Agreement Name,CN=Active Directory Connections,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=domain,DC=com changetype: Modify msExchServer1HighestUSN:1696357 msExchServer1HighestUSNVector:SERVER1:1868357 : SERVER2:2097926 : SERVER3:1696357 : SERVER4:3289482 : SERVER5:3493342 : SERVER6:3523081 : ...

NOTE: The event description contains all of the domain controller names (more than 800 names).

CAUSE

This problem can occur because there is an architectural limit of approximately 800 values (that are not distinguished name-linked) in a multivalued attribute in the Windows 2000 Active Directory. When there are over 800 domain controllers, the ADC attempts to update the msExchServer1HighestUSNVector attribute with the name and update sequence number (USN) number of each domain controller, which does not work because of the architectural limitation.

RESOLUTION

To resolve this problem, obtain the latest service pack for Microsoft Exchange 2000 Server. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

301378 XGEN: How to Obtain the Latest Exchange 2000 Server Service Pack

The English version of this fix should have the following file attributes or later:

Component: Directory

File name	Version
Adc.exe	6.0.5770.18

MORE INFORMATION

After you apply this fix, you must also add the MAX DC State Vector registry value.

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

To add the MAX DC State Vector registry value:

Start Registry Editor (Regedt32.exe).
Locate and click the following key in the registry:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSADC\Parameters
On the Edit menu, click Add Value, and then add the following registry value:
Value name: MAX DC State Vector
Data type: REG_DWORD
Radix: Decimal
Value data: 750
Quit Registry Editor.