Exchange 2003 : System Attendant Service could not be started. DSAccess - Topology Discovery Failed.

Early this morning I received a critical call where the Exchange 2003 Server has went down. Went on site and discovered that the server could not be brought up due to System Attendant service hung during startup.

1. Exchange Server could not be boot into Normal Mode with Exchange System Attendant service enabled.

2. Boot into Safe Mode and disable Exchange System Attendant and Exchange Information Store Service. Reboot and able to boot into Normal Mode.

3. Attempts to start Exchange System Attendant failed. Service could not be started as normal.

4. Event logs > Application logs showing multiple entries of the below errors.

Event Type: Error
Event Source: MSExchangeDSAccess
Event Category: Topology
Event ID: 2114
Date: 10/06/2010
Time: 1:01:14 PM
User: N/A
Computer: MYKLX001
Description:
Process MAD.EXE (PID=4788). Topology Discovery failed, error 0x80040920.

For more information, click http://www.microsoft.com/contentredirect.asp.



Event Type: Error
Event Source: MSExchangeFBPublish
Event Category: General
Event ID: 8213
Date: 10/06/2010
Time: 1:01:14 PM
User: N/A
Computer: MYKLX001
Description:
System Attendant Service failed to create session for virtual machine MYKLX001. The error number is 0xc10306ce.

For more information, click http://www.microsoft.com/contentredirect.asp.




We tried to source solution from the internet. The most direct answer from Google is the below KB.

Exchange services do not start, and event IDs 2114 and 2112 are logged in the Application log in Exchange Server 2003 or in Exchange 2000 Server

This KB assumes that the problem lies with the security access of the Exchange Enterprise Servers Group. Hence the verification on the Default Domain Policy, Default Domain Controller Policy and the User Rights Assignment, and the DomainPrep and so on.

However, we verified the above and even ran the DomainPrep, the problem is still not solved. System Attendant still fails due to Topology Discovery Failure.

**Time is running short as the managers need the emails to be up a.s.a.p**


Without a clue, we were forced to consult Microsoft PSS.
Within 10 minutes, Microsoft engineer discovered the source of the problem.


Within the Exchange Server Netlogon Service Registry lies a Key that record the value of the AD site to be contacted when System Attendant tries to pull data.


HKLM\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters

Key:
DynamicSiteName (REG_SZ) : SITENAME
SiteName (REG_SZ) : SITENAME






2 Days ago, the AD site name was reconfigured. The Exchange Server Netlogon however do not get updated with the new configuration. Hence the System Attendant could not communicate with AD anymore.

As explained by Microsoft, the System Attendant will only encounter problem when the service was restarted and tries to pull data from AD.

New installation of Exchange will automatically configure this registry key. However, when a site name is changed, administrators should verify this Key at the Exchange Server themselves because the Netlogon will not get updated.

As indicated by the engineer,
** This is not documented in any KB articles **


So as soon as we changed the registry to reflect the new site name, System Attendant started and Information Store can be brought up. Email service back online.


So, the next time you wanna reconfigure your AD site, do take note whether the site host any exchange server, and whether the Exchange Server Netlogon Registry Key has been updated with the change.