Teradata database storage space computation

SELECT
SUM(CurrentPerm)/(1024*1024*1024) (DECIMAL(15,6)) (TITLE 'Current Perm size in GB') ,
SUM(MaxPerm)/(1024*1024*1024) (DECIMAL(15,6)) (TITLE 'Max Perm size in GB')
FROM dbc.DiskSpace WHERE DatabaseName='a_database';