Having recently completed an Exchange 2013 deployment for a large organisation that has a global presence, one of the things that came up was having multiple copies of the Offline Address Book with the generating mailboxes for those OABs located in the different datacentres so its closer to the users who are going to use it.
As you know by default there is one OAB and the generating mailbox will exist in one mailbox database only which will be on the first Exchange 2013 server installed.
Prior to Exchange 2013 CU5 Microsoft’s guidance was to only deploy a single OAB generation mailbox per organization but now have better support for multiple OAB mailboxes.
The benefit of this is now you can have the Client Access server retrieve the OAB from the generating mailbox in the same site that the user’s mailbox is in rather than having to traverse an WAN link to get the one and only copy of the OAB from the generating mailbox
The commands used to configure this as shown below:
New-Mailbox -Arbitration -Name "UK OAB Mailbox" -Database UK-DB02-2013 -UserPrincpalName firstname.lastname@example.org –DisplayName "UK OAB Mailbox"
Set-Mailbox "UK OAB Mailbox" –Arbitration –OABGen $true
New-OfflineAddressBook -Name "UK Offline Address Book" –GeneratingMailbox "CN=UK OAB Mailbox,CN=Users,DC=ajheywood,DC=Com" –AddressLists "Default Global Address List"
Set-OfflineAddressBook "UK Offline Address Book" -GeneratingMailbox "CN=UK OAB Mailbox,CN=Users,DC=ajheywood,DC=Com"
Update-OfflineAddressBook "UK Offline Address Book"
For a complete background on this topic and further reading see this article from the Exchange Server team themselves https://blogs.technet.microsoft.com/exchange/2014/05/13/oab-improvements-in-exchange-2013-cumulative-update-5/