It is not difficult to upgrade Berkeley DB 1.85 applications to use the Berkeley DB version 2 library. The Berkeley DB version 2 library has a Berkeley DB 1.85 compatibility mode, which you can use by either recompiling your application's source code or by relinking its object files against the version 2 library.
The underlying databases must be converted, however, as the Berkeley DB version 2 library has a different underlying database format.
As the Berkeley DB 1.85 library did not have an installation target in the Makefile, there's no way to know exactly where it was installed on the system. In addition, many vendors included it in the C library instead of as a separate library, and so it may actually be part of libc and the db.h include file may be installed in /usr/include.
For these reasons, the simplest way to maintain both libraries is to install Berkeley DB version 2 in a completely separate area of your system. The Berkeley DB version 2 installation process allows you to install into a standalone directory hierarchy on your system. See the Building for UNIX platforms documentation for more information and instructions on how to install the Berkeley DB version 2 library, include files and documentation into specific locations.
To replace 1.85 with version 2, you must either convert your 1.85 applications to use the version 2 API or build the Berkeley DB version 2 library to include Berkeley DB 1.85 interface compatibility code. Whether converting your applications to use the version 2 interface or using the version 1.85 compatibility API, you will need to recompile or relink your 1.85 applications, and you must convert any persistent application databases to the Berkeley DB version 2 database formats.
There is no requirement that you recompile your Berkeley DB 1.85 applications, as you can simply link their object files against the Berkeley DB version 2 library.
If you want to recompile your Berkeley DB 1.85 applications, you will have to change them to include the file db_185.h instead of db.h. (The db_185.h file is automatically installed during the Berkeley DB version 2 installation process.) You can then recompile the applications, linking them against the Berkeley DB version 2 library.
For more information on compiling the Berkeley DB 1.85 compatibility code into the Berkeley DB version 2 library, see Building for UNIX platforms.
For more information on converting databases from the Berkeley DB 1.85 formats to the Berkeley DB version 2 formats, see the db_dump185 and db_load documentation.
The name space in Berkeley DB version 2 has been changed from that of previous Berkeley DB versions, notably version 1.85, for portability and consistency reasons. The only name collisions in the two libraries are the names used by the historic dbm, ndbm and hsearch interfaces, and the Berkeley DB 1.85 compatibility interfaces in the Berkeley DB version 2 library.
If you are loading both Berkeley DB 1.85 and Berkeley DB version 2 into a single library, remove the historic interfaces from one of the two library builds, and configure the Berkeley DB version 2 build to not include the Berkeley DB 1.85 compatibility API, otherwise you could have collisions and undefined behavior. This can be done by editing the library Makefiles and reconfiguring and rebuilding the Berkeley DB version 2 library. Obviously, if you use the historic interfaces, you will get the version in the library from which you did not remove it. Similarly, you will not be able to access Berkeley DB version 2 files using the Berkeley DB 1.85 compatibility interface, since you have removed that from the library as well.
Some guidelines and things to watch out for:
Specifically, the partial key match and range search functionality of the R_CURSOR flag in db->seq() has been replaced by the DB_SET_RANGE flag in DBcursor->c_get.
While simply converting Berkeley DB 1.85 function calls to Berkeley DB version 2 function calls will work, we recommend that you eventually reconsider your application's interface to the Berkeley DB database library in light of the additional functionality supplied by Berkeley DB version 2, as it is likely to result in enhanced application performance.