Exchange 2013 data restore and Outlook cached mode RRS feed

  • Question

  • In this scenario the (standalone server) Exchange 2013 database has been successfully restored to a point in time that is "8 hours behind", so there is no need for repair.   Some or all of the Outlook clients were using cached mode before the database needed to be recovered, so they have data up to 8 hours of data that Exchange does not in their OST files.   How will Exchange/Outlook get back in sync with each other?   Would the new data get flushed from the Outlook clients to bring them in sync with the 8 hour old database? Or would there be errors and you would have to disconnect/destroy the OST files for the Outlook clients and rebuild the local cache? Or maybe Exchange is smart enough to know that Outlook has more current data and that its database was just restored, so it will add the new data from the clients to the database...this last scenario is the one I would hope unfolds but I can't find anything to substantiate this with. Thanks in advance!
    Monday, December 14, 2015 6:30 PM

All replies

  • Generally these new items would be added back to the DB... they would have more recent sync series than the restored DB. It's sort of like working offline and importing mail into your mailbox from a PST and then connecting back into Exchange... it will sync back. 

    Also if you still have the log files those would be replayed against the 8 hour old backup and bring you back to the point of failure. 

    Monday, December 14, 2015 6:34 PM
  • Excellent, thanks for this answer!  Do you know this from experience or is there some sort of kb article to reference?  I haven't been able to find a thing.


    Monday, December 14, 2015 6:46 PM
  • Hi,

    Unfortunately, there is no more detailed official documents about whether the messages would be synced from OST file to mailbox after restored from Exchange server backup in your scenario. According to your description, I made a test in my testing environment:

    Firstly, open Outlook and OWA. Then, set outlook works on offline mode. delete some emails from OWA and set outlook back to Cached mode. In this case, those deleted emails which are existed in OST file would be removed from Outlook cached mode instead of syncing back from OST file to the mailbox.

    Therefore, for better and safely consideration, please inform client users to export their emails to .pst file for back up. After Exchange goes online, import these pst file again if there are any missing messages.

    Export Outlook items to an Outlook Data File (.pst):

    Actually, about Exchange 2013 database restore and recovery, there is a feature called  dial tone recovery. By using this feature, exchange allow user send and receive message during database restore. Then, merger the temporary message with former mailbox database.  You can access to the link below for more details:

    Please remember to mark the replies as answers if they help, and unmark the answers if they provide no help. If you have feedback for TechNet Support, contact

    Tuesday, December 15, 2015 3:35 PM
  • Yes, messages deleted from OWA will be deleted in Outlook because there is an action stored as an attribute of the folder in Exchange which tells the client to. That is not the same thing as restoring from a 4 hour old backup where a message was never present. 

    Tuesday, December 15, 2015 4:52 PM
  • It's from experience (~= 15 years worth)... I used to work for a company which made a failover solution for Exchange which ran on a cloud based service and this was generally my experience. Could you potentially do something catastrophic where this wouldn't be true... possibly, but you'd have to really work at it. 

    ... if for example you had a massively corrupt DB and ran essential /p where it did a hard repair on that database you restored during that process it would would mark pages/messages as bad and when the OST synced those would be deleted. But technically running essential /p is what caused the deletes not some gap between data in client and the restored DB. 

    Pro tip: Never run essential /p if you can avoid it. And if you're going to it might be worthwhile to export mail to a PST if necessary not he client. But that is a different/issue than a "simple" delta in time of restored DB and the more recent mail in a client. 

    Tuesday, December 15, 2015 4:57 PM
  • Thanks for all of the feedback on this scenario - short of official documentation, this is sufficient for our needs.


    Wednesday, December 16, 2015 2:59 PM