oracle数据库修改字符集

1.关闭数据库
    [oracle@epm-db-uat ~]$ sqlplus / as sysdba
    SQL*Plus: Release 12.2.0.1.0 Production on Tue Jul 23 09:17:23 2024
    Copyright (c) 1982, 2016, Oracle.  All rights reserved.
    Connected to:
    Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
    SQL> shutdown immediate
    Database closed.
    Database dismounted.
    ORACLE instance shut down.

2.启动数据库到mount
    SQL> startup mount;
    ORACLE instance started.
    Total System Global Area 5.1540E+10 bytes
    Fixed Size		   12174040 bytes
    Variable Size		 1.2616E+10 bytes
    Database Buffers	 3.8789E+10 bytes
    Redo Buffers		  122040320 bytes
    Database mounted.

3.设置session
    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.

4.启动数据库
    SQL> alter database open;
    Database altered.

5.修改字符集
    SQL> ALTER DATABASE CHARACTER SET AL32UTF8
      2  ;
    ALTER DATABASE CHARACTER SET AL32UTF8
    *
    ERROR at line 1:
    ORA-12712: new character set must be a superset of old character set

6.结果报错，提示新字符集必须是老字符集的超集。于是强制转换
    SQL> ALTER DATABASE character set INTERNAL_USE AL32UTF8;
    Database altered.

7.重启数据库，检查字符集
    SQL> shutdown immediate
    Database closed.
    Database dismounted.
    ORACLE instance shut down.
    SQL> startup
    ORACLE instance started.
    Total System Global Area 5.1540E+10 bytes
    Fixed Size		   12174040 bytes
    Variable Size		 1.2616E+10 bytes
    Database Buffers	 3.8789E+10 bytes
    Redo Buffers		  122040320 bytes
    Database mounted.
    Database opened.
    SQL> select * from v$nls_parameters where parameter = 'NLS_CHARACTERSET'
      2  ;
    PARAMETER
    ----------------------------------------------------------------
    VALUE								     CON_ID
    ---------------------------------------------------------------- ----------
    NLS_CHARACTERSET
    AL32UTF8								  0
    SQL>

8.修改成功，确认数据显示正确：中文无乱码