All the gnats user tools honor the GNATSDB environment
variable which is used to determine which database to use. For a local
database, it contains the name of the database to access.
For network access via gnatsd, it contains a colon-separated list of strings that describe the remote database in the form
server:port:databasename:username:password
Any of the fields may be omitted except for server, but at least one colon must appear; otherwise, the value is assumed to be the name of a local database.
If GNATSDB is not set and no command-line options are used to
specify the database, it is assumed that the database is local and that
its name is default.