here's the short article
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Overview
When you upgrade the IBM Lotus Domino Server, the BlackBerry Enterprise Server does not need to be reinstalled.
Additional Information
Before upgrading the IBM Lotus Domino Server, it is recommended that you backup the BlackBerry Configuration Database and the .\Lotus\Domino\Data folder.
For instructions on backing up the BlackBerry Configuration Database, see KB10292.
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When we did it a few months ago, we stopped Blackberry Services, then Domino services, made a copy of the Blackberry folder under the Domino Data directory (where the state databases are kept).
Then upgraded Domino.
Started the Domino service
Started the Blackberry services
and it hummed a long nicely.