While the C API changes are extensive, they are also simple to understand. No functionality was removed. The changes required comparatively few modifications to the C++ and Java APIs, mostly limited to moving methods among classes and the addition of a new flag value to a few interfaces. For specific instructions on upgrading Berkeley DB 2.X applications to this release, see the "Upgrading Berkeley DB 2.X.X applications to Berkeley DB 3.0" chapter in the Berkeley DB Reference Guide.
The following individual changes are all part of this larger change.