更改步骤：1、用sysdba角色用户登录sqlplus: 命令行输入：sqlplus sys as sysdba

               2、输入口令，进入sqlplus：sql>---

               3、依次键入下面的命令行执行：

                    shutdown immediate;
                    STARTUP MOUNT;
                    ALTER SESSION SET SQL_TRACE=TRUE;
                    ALTER SYSTEM ENABLE RESTRICTED SESSION;
                    ALTER SYSTEM SET JOB_QUEUE_PROCESSES=0;
                    ALTER SYSTEM SET AQ_TM_PROCESSES=0;
                    ALTER DATABASE OPEN;
                    ALTER DATABASE character set INTERNAL_USE AL32UTF8;
                    ALTER SESSION SET SQL_TRACE=FALSE;
                    shutdown immediate;
                    startup;

风险分析：执行上述命令，有可能造成数据库中已有数据混乱的情况，所以在进行操作前，

               要进行数据库的备份操作；

结果查看：察看 NLS_LANG 信息：
               SELECT parameter, value FROM v$nls_parameters WHERE parameter LIKE '%CHARACTERSET';
              NLS_LANG 信息已经变成：

              NLS_CHARACTERSET
              AL32UTF8
              NLS_NCHAR_CHARACTERSET
              AL16UTF16