How to check character set in Oracle

SELECT value$ FROM sys.props$ WHERE name = ‘NLS_CHARACTERSET’ ; SELECT * FROM NLS_DATABASE_PARAMETERS select owner, table_name, column_name      from dba_tab_columns     where (data_type = ‘NCHAR’ or             data_type = ‘NVARCHAR2’ or             data_type = ‘NCLOB’) and             owner != ‘SYS’ and             owner != ‘SYSTEM’;