A clear understanding of how the offline address book works in exchange helps an admin in troubleshooting the related issues. This article explains how oab works in the 2007 edition.
The Exchange System Attendant service is responsible for the generation of oab. This service is available only on a server that has the mailbox role installed. The SA invokes a dll file called oabgen.dll. To find out the server that is generating the offline address book, launch EMC –> Organizational Configuration –> Mailbox –> OAB tab.
Once you have made too many changes in exchange, you can update the address book by right clicking and selecting Update. By default, oab is updated only once in 24 hours at 5am. You can customize the update schedule depending upon your requirements.
Where exactly are these oab files stored? On a default installtion, the oab files are stored in C:Program FilesMicrosoftExchange ServerExchangeOAB. This folder is shared so that it can be replicated to the CAS server for web distribution.
How does oab end up in public folders? Outlook 2003 and previous versions get oab from the system public folders in exchange. The oab generation server opens the oab folders and updates the file. The oabgen.dll file is responsible for connecting to the public folder.
How does Outlook 2007 get oab files? The server that has the client access role installed (CAS server) is responsible for providing oab files for outlook 2007 clients. For that, CAS server runs a service named Microsoft Exchange File Distribution Service which copies the oab files from the mailbox server (ExchangeOAB folder) to the web distribution point in the CAS server.
Where is this web distribution point, one might ask? The web distribution folder is a folder in the file system where the copied oab files are placed. The default location is C:Program FilesMicrosoftExchange ServerClientAccessOAB.
The web distribution point is updated once in 8 hours. If you want to force an oab update, restart the Exchange File Distribution Service.
Now that you know how oab works and are replicated from the mailbox server to the system folders and web distribution point, you will find it much easier to troubleshoot any issues relating to the offline address book.