Character set

col PROPERTY_VALUE format a30
col DESCRIPTION format a40
select * from database_properties where property_name like '%SET';
PROPERTY_NAME PROPERTY_VALUE DESCRIPTION
------------------------------ ------------------------------ -----------------------NLS_CHARACTERSET AL32UTF8 Character set
NLS_NCHAR_CHARACTERSET AL16UTF16 NCHAR Character set

SQL CHAR datatypes:
CHAR, VARCHAR2, CLOB, LONG
Unicode datatypes:
NCHAR, NVARCHAR2, NCLOB

NLS Parameter Setting Precedence
1, Set in SQL function (Current SQL funciton)
2, Explicit ALTER SESSION statement (Current session)
3, Client environment variable (implicit ALTER SESSION statement) (Current session)
4, Set by server initialization parameter (Instance)
5. Default (Instance)