測試資料庫的NLS_NCHAR_CHARACTERSET和正式環境不一致，需要由UTF8修改為AL16UTF16。

1、停資料庫

SQL> alter system checkpoint;

System altered.

SQL> alter system checkpoint;

System altered.

SQL> alter system switch logfile;

System altered.

SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.

2、啟動資料庫
SQL> STARTUP MOUNT EXCLUSIVE;
ORACLE instance started.

Total System Global Area  838860800 bytes
Fixed Size                  2024536 bytes
Variable Size             192940968 bytes
Database Buffers          637534208 bytes
Redo Buffers                6361088 bytes
Database mounted.
SQL> alter system enable restricted session;

System altered.

SQL> alter system set job_queue_processes=0;

System altered.

SQL> alter system set aq_tm_processes=0;

System altered.

SQL> alter database open;

Database altered.

SQL> ALTER DATABASE NATIONAL CHARACTER SET INTERNAL_USE AL16UTF16;

Database altered.

注意：

1）這樣修改會影響資料庫中定義了Nclob、NVARCHAR2等大欄位的表，會出現亂碼。需要重新匯入表，當然在修改前要備份相關表。

2）如果沒有大物件，在使用過程中進行語言轉換沒有什麼影響，（切記設定的字符集必須是ORACLE支援，不然不能start）

若直接執行

ALTER DATABASE NATIONAL CHARACTER SET AL16UTF16;

也可以,但是可能會出現‘ORA-12717: Cannot ALTER DATABASE NATIONAL CHARACTER SET when
NCLOB data exists’ 這樣的提示資訊

報錯資訊如下：

Wed May 30 16:25:58 2012
alter database national character set AL16UTF16
Wed May 30 16:25:58 2012
 XDB.XDB$NMSPC_ID (NMSPCURI) - NVARCHAR2 populated
ORA-12717 signalled during: alter database national character set AL16UTF16...

3、在停資料庫時hang住了，沒有辦法只有直接abort了再startup。

SQL> shutdown immediate;
ORA-03113: end-of-file on communication channel

SQL> exit

SQL> connect /as sysdba
Connected to an idle instance.
SQL> shutdown abort;
ORACLE instance shut down.
SQL> exit