When you update the offline address book by using the Update-OfflineAddressBook command or by using a scheduled task, the following event (Event ID 9373) is logged in the Application log on a computer that is running Microsoft Exchange Server 2007:
Event Type: Error
Event Source: MSExchangeSA
Event Category: OAL Generator
Event ID: 9373
Description: OALGen detected that the file '\\<SERVER name>\ExchangeOAB\<folder name>\a58e388b-7b23-4944-b042-58a7d0c6590f-data-1.lzx' is corrupted or missing. This indicates data tampering or disk problems. Restore files in this folder from the recent backup or clean up folder content and force a full OAB generation. - Default Offline Address Book
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
The reason this happens is that that when one or more OAB Version 4 offline address book files are corrupted or missing. In this case, the Microsoft Outlook clients cannot download the updated files until the issue is resolved. This can happen for quiet a few reasons:
- Virus scanning the OAB Virtual Directory on the (CAS) Client Access Server
- Disk problems. Some of the disk sectors that are containing the OAB files become corrupted
- Permissions problems on the files in the \\ExchangeInstallDir\ExchangeOAB\OAB GUID directory have changed
- By default, below accounts should have following Share and Security permissions on ExchangeOAB folder:
- SYSTEM” account should have “Full Control” permissions
- “Exchange Servers” group should have “Read Only”
- Local “Administrators” group should have “Full Control” permissions.
- All of the OAB files have *not* been replicated to the (CAS) Client Access Server. For more information on this please see the following blog: http://blogs.msdn.com/dgoldman/archive/2006/08/25/How-Exchange-2007-OAB-Files-are-replicated-to-a-Client-Access-Server-for-download.aspx
There are 3 fixes for this. To resolve this issue, use one of the following methods.
Method 1: Restore the contents of the OABGenation folder
If daily backups are available, restore the contents of the OABGen folder to the following folder:
ExchangeInstallDir \ExchangeOAB\ OAB GUID
Note ExchangeInstallDir is a placeholder for the name of the Exchange Server 2007 installation directory. OAB GUID is a placeholder for the name of the folder.
Method 2: Rebuild the OAB files by using Exchange Management Console or the Exchange Management Shell
If the corrupted offline address book item is enabled for public folders distribution, and if the data was published in public folders before the offline address book item was corrupted, delete the contents of the OABGen folder from the ExchangeInstallDir \ExchangeOAB\ OAB GUID folder. Then, rebuild the offline address book files by using one of the following methods:
• Use Exchange Management Console to rebuild the offline address book files. To do this, follow these steps:
1. Open Exchange Management Console.
2. Expand Organization Configuration, and then expand Mailbox.
3. On the details panel, click Offline Address Book, and then select the offline address book item that you want to update.
4. On the Action panel, click Update, and then click Yes.
• Use the Update-OfflineAddressBook command to rebuild the offline address book files.
To do this, run the following command in the Exchange Management Shell.
Update-OfflineAddressBook <OAB GUID>
Note You can run the Update-OfflineAddressBook command on a computer that has the Mailbox, Client Access, or Hub Transport server role installed. To do this, you must log on by using an account that is a member of the Exchange Organization Administrators group. The account must also be a member of the local Administrators group on that computer.
Method 3: Rebuild the offline address book files by using a command
If neither daily backups nor public folders distribution is available, delete the contents of the OABGen folder from the ExchangeInstallDir \ExchangeOAB\ OAB GUID folder. Then, rebuild the offline address book files by using one of the following commands.
Update-OfflineAddressBook -Identity MyOAB
Note In this example, the Update-OfflineAddressBook command is used to update the offline address book file that is named MyOAB.
Update-OfflineAddressBook <OAB GUID>
Note When you use this command, the offline address book will be rebuilt. This will cause all clients to process a full offline address book download. For OAB Version 2 and OAB Version 3a, a full offline address book download can cause massive network traffic between client access servers and clients.