exchange 2010 database

I am gettng below message on my exchange 2010 server. Does any one know how to check maintenance window in Exchange 2010 and how to resolve the below warning


Information Store (7484) Mailbox Database 1918073711: Database 'H:\Exchange2010\Mailbox\Mailbox Database 1918073711\Mailbox Database 1918073711.edb': While attempting to move to the next or previous node in a B-Tree, the database engine skipped over 10499 non-visible nodes in 55 pages. 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 are yet to be purged from the database.
      Name: DVU-1-2F
      Owning Table: DVU-1-2F
      ObjectId: 16273
      PgnoRoot: 612733
      Type: 2
      Unversioned Deletes: 0
      Uncommitted Deletes: 0
      Committed Deletes: 10499
      Non-Visible Inserts: 0

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