The database package from Berkeley is called
It contains hash and btree routines and gets rid of many of the
limitations that exist in earlier database versions (such as dbm(3)
and ndbm(3)). If your site has, or expects to have, huge
alias(5) files - say 2000 lines or more - or
many database files, you should consider db
to be mandatory. This new database is also recommended because its
accesses and updates are considerably faster.