Berkeley DB Reference Guide:
  Upgrading Berkeley DB Applications

Release 2.0: upgrade requirements

You will need to upgrade your on-disk databases, as all access method database formats changed in the Berkeley DB 2.0 release. For information on converting databases from Berkeley DB 1.85 to Berkeley DB 2.0, see the db_dump185 and db_load documentation. As database environments did not exist prior to the 2.0 release, there is no question of upgrading existing database environments.

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