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.





ranjeet August 27, 2009 at 5:22 pm
Excellently explained article. Full Marks!
-Ranjeet
Rajith Jose Enchiparambil August 27, 2009 at 8:03 pm
Thanks Ranjeet.
Anonymous October 14, 2009 at 9:10 am
Good, straightforward article, just what i've been looking for! Thank you!
Rajith Jose Enchiparambil October 14, 2009 at 4:06 pm
Thanks Anonymous.
Anonymous October 30, 2009 at 3:31 am
nice
Rajith Jose Enchiparambil October 30, 2009 at 6:51 pm
Thanks Anonymous
Sanjay April 6, 2010 at 8:43 pm
wow….simple and very clear…thank you so much
Rajith Jose Enchiparambil April 12, 2010 at 3:32 pm
Thanks Sanjay.
Anonymous October 8, 2010 at 10:55 am
I have done all the steps but i amnot able to download OAB on outlook client. it stated an error "Microsoft Exchange object not found"
Rajith Jose Enchiparambil October 8, 2010 at 11:05 am
Hi,
Is it Exchange 2007 or 2010 & which Outlook version?
Anonymous October 15, 2010 at 1:31 pm
it is exchange 2007 sp3 with Hub/CAS nlb on two nodes & SCC mailbox cluster and outlook version is 2007.
Rajith Jose Enchiparambil October 15, 2010 at 2:17 pm
If you right click Outlook icon in the system tray (holding the Ctrl key down)and run "Test Email COnfiguration", is it showing the correct urls for all Exchange webs ervices?
Anonymous October 16, 2010 at 11:18 am
No .. it said autodiscover error….
Rajith Jose Enchiparambil October 16, 2010 at 3:36 pm
That's the reason. You need tto set all Exchange urls.
Anonymous October 18, 2010 at 11:03 am
Ok…can you tell me where i will set these exchange urls
Rajith Jose Enchiparambil October 18, 2010 at 11:37 am
Check http://technet.microsoft.com/en-us/library/bb201695.aspx and http://www.msexchange.org/articles_tutorials/exchange-server-2007/management-administration/configuring-exchange-server-2007-web-services-urls.html
Anonymous December 23, 2010 at 3:10 pm
If I need to download all my Offline Address Book entries onto a file, without Outlook, just a plain test program to cache all the Global Address List entries, how can I achieve that?
ResolveNames gets me the entries with a live search, but I need them cached in my application.
Anonymous February 17, 2011 at 8:07 pm
Excellent Article
Rajith Jose Enchiparambil February 18, 2011 at 9:05 am
Thanks
BhaskarBalivada July 10, 2012 at 10:01 am
Very use full article, thank you very much
Rajith Enchiparambil July 16, 2012 at 1:06 pm
Thanks Bhaskar
Muthupandi August 23, 2012 at 5:49 am
Very good to know the ground level knowledge of OAB. Thanks Rajith
Rajith Enchiparambil September 17, 2012 at 10:24 am
Pleasure is mine Muthupandi
riteshcpatil@yahoo.co.in September 17, 2012 at 2:07 pm
excellent article
Rajith Enchiparambil September 17, 2012 at 8:46 pm
Thanks Ritesh.