Orphaned Offline Address Book Recovery in Exchange Server 2010

As the name suggest, an Offline Address Book (OAB) is a collection of address list downloaded by the client offline or in Cached Exchange Mode. By default, Exchange creates and updates the OAB daily between 5:00-5:15 AM. We can change these settings and can also specify the originating Mailbox server for each OAB. The originating OAB server generates new OAB file, compress them and place them on a local share for further distribution.

When an OAB is not updated for at least 25 hours, it is called orphaned. Orphaned OAB Recovery is a part of OAB maintenance; the objective of OAB recovery is to recover the orphaned offline address book. The orphaned time is calculated based on the LastTouchedTime and Schedule properties of the OAB.

In Exchange organization, only one Exchange 2010 Mailbox server is selected to perform the Orphaned OAB Recovery; and other servers knows which server is performing recovery.  Exchange Server 2010 automatically executes the Move-OfflineAddressBook command to move the orphaned OAB to the selected Mailbox server. Orphaned OAB can also be moved manually by running the Move-OfflineAddressBook command or from the EMC.

How to move the OAB to another server

Below command will move the OAB “My OAB” to the server Exch01:

Move-OfflineAddressBook -Identity "My OAB" -Server Exch01

All Exchange 2010 mailbox servers will log event ID 2001 in the Application event log, indicating that evaluation of OAB recovery has taken place:

Log Name: Application
Source: MSExchange OAB Maintenance
Event ID: 2001
Task Category: Orphaned OAB Recovery
Level: Information
Description:
The server responsible for performing the OAB recovery scan is <server>.

Event ID 2002 is logged on all Exchange 2010 Mailbox servers that are not selected to do OAB recovery:

Log Name: Application
Source: MSExchange OAB Maintenance
Event ID: 2002
Task Category: Orphaned OAB Recovery
Level: Information
Description:
Because this server is not the one responsible for performing the OAB recovery scan, the task is exiting.

Events 2003 and 2004 are loggedOn the Exchange 2010 Mailbox server that is selected to perform OAB recovery:

Log Name: Application
Source: MSExchange OAB Maintenance
Event ID: 2003
Task Category: Orphaned OAB Recovery
Level: Information
Description:
Orphaned OAB recovery scan has begun.

Log Name: Application
Source: MSExchange OAB Maintenance
Event ID: 2004
Task Category: Orphaned OAB Recovery
Level: Information
Description:
Orphaned OAB recovery scan has been completed.

Event ID 2005 is generated on selected server if no orphaned offline address books are detected:

Log Name: Application
Source: MSExchange OAB Maintenance
Event ID: 2005
Task Category: Orphaned OAB Recovery
Level: Information
Description:
No orphaned offline address books were found.

Event ID 2006 is generated on the selected Mailbox server when an orphaned OAB has been detected:

Log Name: Application
Source: MSExchange OAB Maintenance
Event ID: 2006
Task Category: Orphaned OAB Recovery
Level: Warning
Description:
<number of orphaned OAB detected> orphaned offline address books were found. The OAB Maintenance Servicelet will attempt to move these offline address books to functioning servers.

Then Recover Orphaned OAB Process is executed on the selected server and event ID 2007 is logged for each orphaned OAB detected:

Log Name: Application
Source: MSExchange OAB Maintenance
Event ID: 2007
Task Category: Orphaned OAB Recovery
Level: Information
Description:
The offline address book \Default Offline Address Book was successfully moved to server <MBX server>.