On my Exchange 2007 server, I ran TSM as backup client. TSM was scheduled to backup every night at 11 pm., In the mean while, I had scheduled the online maintenance in Exchange 2007 daily from 0am to 7am.
The following error occured every day in my event viewer
Event Type: Warning
Event Source: MSExchangeIS Mailbox Store
Event Category: Background Cleanup
Event ID: 9871
Time: 7:00:00 AM
Computer: %server name%
There is an online maintenance overlap for database “maildb1″. Please revise the online maintenance schedule. For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
It seemed that the online maintenance schedule was overlapping TSM every night, which resulted in event 9871. TSM needed 1:15h to complete the backup.
After rescheduling the online maintenance to 1am to 7am, the error disappeared.