select parameter,value from nls_database_parameters;

PARAMETER                                        VALUE
----------------------------------------         ----------------------------------------
NLS_LANGUAGE                               AMERICAN
NLS_TERRITORY                              AMERICA
NLS_CURRENCY                              $
NLS_ISO_CURRENCY                     AMERICA
NLS_NUMERIC_CHARACTERS      .,
NLS_CHARACTERSET                     AL32UTF8
NLS_CALENDAR                               GREGORIAN
NLS_DATE_FORMAT                         DD-MON-RR
NLS_DATE_LANGUAGE                   AMERICAN
NLS_SORT                                           BINARY
NLS_TIME_FORMAT                           HH.MI.SSXFF AM

PARAMETER                                         VALUE
----------------------------------------       -  ---------------------------------------
NLS_TIMESTAMP_FORMAT               DD-MON-RR HH.MI.SSXFF AM
NLS_TIME_TZ_FORMAT                     HH.MI.SSXFF AM TZR
NLS_TIMESTAMP_TZ_FORMAT        DD-MON-RR HH.MI.SSXFF AM TZR
NLS_DUAL_CURRENCY                    $
NLS_COMP                                            BINARY
NLS_LENGTH_SEMANTICS               BYTE
NLS_NCHAR_CONV_EXCP               FALSE
NLS_NCHAR_CHARACTERSET       AL16UTF16
NLS_RDBMS_VERSION                     10.2.0.1.0

20 rows selected.
NLS_CHARACTERSET是数据库字符集，NLS_NCHAR_CHARACTERSET是国家字符集

ORACLE中有两大类字符型数据，VARCHAR2是按照数据库字符集来存储数据。而NVARCHAR2是按照国家字符集存储数据的。同样，CHAR和NCHAR也一样，一是数据库字符符，一是国家字符集。
字符集不同，二进制码的组合就不同。
比如有一串二进制信息：1101,0110,1101,0000,1011,1001,1111,1010，按照16位双字节GBK字符集理解，可以代表“中国”两个字。如果单字节的字符集，这一串二进制代表ASC码为214、208、185、250的四个怪字符。
这就是字符集的作用，就是以什么样的形式理解信息。

select NAME,VALUE$,COMMENT$ from props$;

NAME                           VALUE$                                   COMMENT$
------------------------------ ---------------------------------------- --------------------------------------------
DICT.BASE                      2                                        dictionary base tables version #
DEFAULT_TEMP_TABLESPACE        TEMP                                     Name of default temporary tablespace
DEFAULT_PERMANENT_TABLESPACE   USERS                                    Name of default permanent tablespace
DEFAULT_TBS_TYPE               SMALLFILE                                Default tablespace type
NLS_LANGUAGE                   AMERICAN                                 Language
NLS_TERRITORY                  AMERICA                                  Territory
NLS_CURRENCY                   $                                        Local currency
NLS_ISO_CURRENCY               AMERICA                                  ISO currency
NLS_NUMERIC_CHARACTERS         .,                                       Numeric characters
NLS_CHARACTERSET               AL32UTF8                                 Character set
NLS_CALENDAR                   GREGORIAN                                Calendar system

NAME                           VALUE$                                   COMMENT$
------------------------------ ---------------------------------------- --------------------------------------------
NLS_DATE_FORMAT                DD-MON-RR                                Date format
NLS_DATE_LANGUAGE              AMERICAN                                 Date language
NLS_SORT                       BINARY                                   Linguistic definition
NLS_TIME_FORMAT                HH.MI.SSXFF AM                           Time format
NLS_TIMESTAMP_FORMAT           DD-MON-RR HH.MI.SSXFF AM                 Time stamp format
NLS_TIME_TZ_FORMAT             HH.MI.SSXFF AM TZR                       Time with timezone format
NLS_TIMESTAMP_TZ_FORMAT        DD-MON-RR HH.MI.SSXFF AM TZR             Timestamp with timezone format
NLS_DUAL_CURRENCY              $                                        Dual currency symbol
NLS_COMP                       BINARY                                   NLS comparison
NLS_LENGTH_SEMANTICS           BYTE                                     NLS length semantics
NLS_NCHAR_CONV_EXCP            FALSE                                    NLS conversion exception

NAME                           VALUE$                                   COMMENT$
------------------------------ ---------------------------------------- --------------------------------------------
NLS_NCHAR_CHARACTERSET         AL16UTF16                                NCHAR Character set
NLS_RDBMS_VERSION              10.2.0.1.0                               RDBMS version for NLS parameters
GLOBAL_DB_NAME                 DBTEST.REGRESS.RDBMS.DEV.US.ORACLE.COM   Global database name
EXPORT_VIEWS_VERSION           8                                        Export views revision #
DBTIMEZONE                     00:00                                    DB time zone

27 rows selected.