Required values for $params:
'phptype' The database type (e.g. 'pgsql', 'mysql', etc.). 'hostspec' The hostname of the database server. 'protocol' The communication protocol ('tcp', 'unix', etc.). 'username' The username with which to connect to the database. 'password' The password associated with 'username'. 'database' The name of the database. 'table' The name of the tasks table in 'database'.
Required by some database implementations: 'options' Additional options to pass to the database. 'tty' The TTY on which to connect to the database. 'port' The port on which to connect to the database.
The table structure can be created by the scripts/drivers/nag_tasks.sql script.