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

# Release 3.1: on-disk database format

Finally, you will need to upgrade your on-disk databases, as all of the Berkeley DB database formats changed in the Berkeley DB 3.1 release. (The on-disk Btree/Recno format changed from version 7 to version 8. The on-disk Hash format changed from version 6 to version 7. The on-disk Queue format changed from version 1 to version 2.)

An additional flag, DB_DUPSORT, has been added to the DB->upgrade function for this upgrade. Please review the DB->upgrade documentation for further information.

Until the underlying databases are upgraded, the DB->open function will return a DB_OLD_VERSION error.

For further information on upgrading database formats, see "Upgrading databases".

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