### Berkeley DB Reference Guide: Upgrading Berkeley DB Applications |

# Release 3.0: upgrade requirements

Log file formats and the Btree, Recno and Hash Access Method database formats changed in the Berkeley DB 3.0 release. (The on-disk Btree/Recno format changed from version 6 to version 7. The on-disk Hash format changed from version 5 to version 6.) Until the underlying databases are upgraded, the DB->open function will return a DB_OLD_VERSION error.

For further information on upgrading Berkeley DB installations, see Upgrading Berkeley DB installations.

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