Friday, 21 January 2011

OAB Delta Changes

I've just been troubleshooting an issue involving the OAB on Exchange 2010.  Scenario : on a single Exchange 2010 SP1 UR2 server running the Mailbox, Client Access Server and Hub Transport roles, an administrator creates a new distribution group that is urgently required, updates the OAB in the Exchange Management Console and then informs the end-user to download the OAB from within Outlook.  The result?  The distribution group is still not showing in Outlook.  The end-user confirms that he can see the group in OWA.  Why is this?

Well, I have written a long 4-part article on the overall OAB process that you can access here.  The short answer is not to forget the process that copies the updated OAB files from the Mailbox role to the Client Access Server role ready for web-based distribution.  Even though the administrator has updated the OAB within the Exchange Management Console, Exchange still has to copy these files to the OAB virtual directory folder where the Outlook client will pick them up.  Of course, I'm assuming that the Outlook client is capable of web-based distribution here, rather than public folder distribution.

By default, this copy process runs every 480 minutes.  To see this, run this cmdlet:

Get-OabVirtualDirectory | fl poll*

This will show the PollInterval parameter for all OAB virtual directories and you should see 480 minutes as the default setting.  You can change this value of course, or you can run a one-off copy process via this cmdlet:

Update-FileDistributionService -Identity {server} -Type OAB

That will force the Microsoft Exchange File Distribution service to copy the updated OAB files generated by the Mailbox role to the OAB virtual directory location.  Then get the end-user to download the OAB again.

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