We keep getting event 629 on one of our mailbox DB. The online maintenance window of this DB is set to everyday 1:00AM-5:00AM. Should I widen the online maintenance window or is there something else I need to look at? We are running EXCH2010 SP3 RU8v2. The DB is in a DAG.

Information Store (6552) CorpUserDB: Database 'G:\CorpUserDB\CorpUser.edb': While attempting to move to the next or previous node in a B-Tree, the database engine skipped over 11719 non-visible nodes in 46 pages. In addition, since this message was last reported 1 hours ago, 3 other incidents of excessive non-visible nodes were encountered (a total of 42982 nodes in 168 pages were skipped) during navigation in this B-Tree. It is likely that these non-visible nodes are nodes which have been marked for deletion but which are yet to be purged. The database may benefit from widening the online maintenance window during off-peak hours in order to purge such nodes and reclaim their space. If this message persists, offline defragmentation may be run to remove all nodes which have been marked for deletion but have yet to be purged from the database.
 Name: MSysObjects
 Owning Table: MSysObjects
 ObjectId: 2
 PgnoRoot: 4
 Type: 2
 Unversioned Deletes: 11719
 Uncommitted Deletes: 0
 Committed Deletes: 0
 Non-Visible Inserts: 0

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Hi,

Please try to expand the maintenance window, wait for the completion of the online maintenance and see if this warning goes away.

If you have less no of users and small database, you can consider to create a new database and move the mailbox from that database to new database. This method solved the same event in other similar thread in my experience.

For reference:

https://social.technet.microsoft.com/Forums/en-US/1c07128e-7b9f-4594-8c0e-9079ea2733ca/event-id-629?forum=exchangesvrgenerallegacy

Best Regards.