db4 - The Berkeley DB database library (version 4) for C.
The Berkeley Database (Berkeley DB) is a programmatic toolkit that
provides embedded database support for both traditional and
client/server applications. The Berkeley DB includes B+tree, Extended
Linear Hashing, Fixed and Variable-length record access methods,
transactions, locking, logging, shared memory caching, and database
recovery. The Berkeley DB supports C, C++, Java, and Perl APIs. It is
used by many applications, including Python and Perl, so this should
be installed on all systems.