# Berkeley DB Reference Guide: Release 4.1: upgrade requirements
Berkeley DB: An embedded database programmatic toolkit.
Keywords: embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++

Berkeley DB Reference Guide:
  Upgrading Berkeley DB Applications

Release 4.1: upgrade requirements

The log file format changed in the Berkeley DB 4.1 release.

All of the access method database formats changed in the Berkeley DB 4.1 release (Btree/Recno: version 8 to version 9, Hash: version 7 to version 8, and Queue: version 3 to version 4). The format changes are entirely backward-compatible, and no database upgrades are needed. Note that databases created using the 4.1 release may not be usable with earlier Berkeley DB releases.

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

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