Hi This post is just for information only and maybe helpful to anyone who experience the similiar issue. While running schema upgrade prepareAD failed with follwoing error.Exchange 2007 SP2 with Windows 2008 Organization Preparation ......................... FAILEDActive Directory operation failed on dc01.xyz.com. The object 'CN=Address Lists Container,CN=exchange,CN=Microsoft Exchange,CN=Services,CN=Confi guration,DC=xyz,DC=com' already exists.Also we noticed the Exchange orgnaization information in the configuration conatiner has been disappered after this. ExBPA and ADSIEDIT confirmed that there is no exchange information exists in AD. We cannot run the setup again as it fails with same error. But noticed thatexisting Exchange servers were up and running.Resolution -Problem happeneddue to some permission issues happened in AD after the failed schema upgrade. Restoring the permissions to the defaultfor exchange configuration container resolved the issue. used the following command"DSACLS "CN=Exchange Orgnaization,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=xyz,DC=com" /S" Regards, Arif Arif

Thank you Arif.It really would be helpful to others.I will change the type of this thread to comment.Thanks again.Xiu

Using these instructions -> http://www.howexchangeworks.com/2009/08/upgrading-exchange-2007-ccr-to-sp2.html Environment: 2 Mailstore servers in CCR configuration1 HUB/CAS1 Edge1 AD HUB/CAS and EDGE Upgraded secessfully. On Mailstore servers in CCR configuration First ran SP2 on the passive node in the cluster with setup /m:upgrade secessfull, But setup /UpgradeCMS Failed with following Error:[PS] E:\Exchange SP2\E2K7SP2EN64>setup /UpgradeCMS Welcome to Microsoft Exchange Server 2007 Unattended SetupPreparing Exchange SetupThe following server roles will be upgraded Clustered Mailbox ServerPerforming Microsoft Exchange Server Prerequisite CheckConfiguring Microsoft Exchange Server Clustered Mailbox Server ......................... FAILED Active Directory server xxxx.xxxx.com is not available. Error message:A local error occurred.The Exchange Server Setup operation did not complete. For more information, visit http://support.microsoft.com and enter the Error ID.Exchange Server setup encountered an error. Now my HUB/CAS and EDGE is working fine with SP2 however my cluster mailbox are not able to upgrade SP2.Inspite of this my exchange server is working fine. After this I tried to troubleshoot on the cluster mailbox with setup /prepareschema and the result as below: [PS] E:\Exchange SP2\E2K7SP2EN64>.\setup /prepareschema Welcome to Microsoft Exchange Server 2007 Unattended Setup Preparing Exchange Setup No server roles will be installed Performing Microsoft Exchange Server Prerequisite Check Organization Checks ......................... COMPLETED Configuring Microsoft Exchange Server Extending Active Directory schemaProgress ......................... FAILEDActive Directory server XXXXXX.DOMAIN.com is not available. Error message:The LDAP server returned an unknown error. The Exchange Server Setup operation did not complete. For more information, visit http://support.microsoft.com and enter the Error ID. Exchange Server setup encountered an error.I would be really greatful if you please help me to resolve this problem.