OAB File ReplicationIn prior versions of Exchange the Offline Address List files would reside in the form of an OAB message and attachments. In Exchange 2007 the Offline Address List files can reside in a few places: - In a public folder in the public folder information store (if client legacy support is specified)
- On the OAB Generation Server (local distribution point)
- On multiple distribution points (Other CAS servers).
This is really important to understand because if you are not aware of where these files reside or how they get to the other servers you will not know were to start troubleshooting. Following FDS replication of an Offline Address List
The FDS (File Distribution Service) is the component that is responsible for the replication of OAB files. This service resides on the CAS (Client Access Servers). The FDS will contact the Active Directory once it's polling frequency has been hit (default 480 minutes), or if a notification has been sent to FDS to state otherwise: - A new Offline Address Book has been created
- An Offline Address Book needs to be published
- The polling interval has been changed or the polling interval is up
- The file paths change
- OAB Generation server changes
There are a few key things that I need to point out before we go further. 1. By default this OAB share (local distribution point) will not be present. This gets created the first time the OAB Generation creates a Version 4 Offline Address List. This can be by a manual rebuild or when the Default scheduled time is up (5am).
2. Once the Distribution Point share has been created it will contain sub directories. Each sub directory will be named with the the GUID of the Offline Address Book.
3. Each OAB directory will contain a set of files that will be downloaded by the client.
4. All files in the directory will be specified in the oab.xml file. This is the file that the Outlook client will look at so it can determine which files it must use. If these files or directories are not present this can result in an Outlook client synchronization errors as there will be nothing for the client to download. The process from start to finish
1. The OAB Generation Servers generates an Version 4 Offline Address List. At the end of the generation the files will reside in the System Attendant Mailbox as this is the master location.
2. The files are then copied from the System Attendant Mailbox to the local distribution share on the OAB Generation Server. A. Internal Location = C:\Program Files\Microsoft\Exchange Server\ExchangeOAB
B. Network share location = \\E12-MBX\ExchangeOAB At this point the files can be downloaded from the OAB Generation Server by an Outlook client. 3. A notification is sent to the FDS service on the Client Access Server.
4. The FDS will then start replication of the files to the remote distribution points where they may be. Below is a copy of the information event that you will see on the Client Access Server when an Offline Address List has been successfully replicated. Event Type: Information
Event Source: MSExchangeFDS
Event Category: FileReplication
Event ID: 1008
Date: 8/25/2006
Time: 6:05:41 PM
User: N/A
Computer: E12-CAS
Description:
Process MSExchangeFDS.exe (PID=620). Offline Address Book data synchronization task has completed successfully. OAB name: "Test", Guid: 1fd83cb9-8887-4bbd-83f2-59c8a5ab29a4 For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp | 
