...This provides an alternative location for storing configuration information used by the Name Service Switch libraries, and may be used to supplement user, group and other information in a Berkeley DB.
The Berkeley DB NSS module provides an alternative means for storing configuration information traditionally kept in several plain-text files in /etc (e.g. /etc/passwd). The module uses the Berkeley DB Library to store this information in several database files in /var/db (e.g. /var/db/passwd.db). Using these databases can lead to a considerable speed-up if the files in /etc are large (e.g. on a system with a lot of accounts). The databases may also be used as a local cache for network accounts, or as a means to supplement or override UIDs, GIDs, home directories etc. provided by network accounts.