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.