本方法根据我目前掌握的知识只能应用于新库，有数据的库不建议使用
SQL> shutdown immediate Database closed. Database dismounted. ORACLE instance shut down. SQL> startup mount; ORACLE instance started. Total System Global Area 918618112 bytes Fixed Size 2258640 bytes Variable Size 549456176 bytes Database Buffers 360710144 bytes Redo Buffers 6193152 bytes Database mounted. SQL> alter session set sql_trace=true; Session altered. 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 character set INTERNAL_USE UTF8; Database altered. SQL> update props$ set VALUE$='UTF8' where NAME='NLS_NCHAR_CHARACTERSET'; 1 row updated. SQL> commit ; Commit complete. SQL> shutdown immediate Database closed. Database dismounted. ORACLE instance shut down. SQL> startup ORACLE instance started. Total System Global Area 918618112 bytes Fixed Size 2258640 bytes Variable Size 549456176 bytes Database Buffers 360710144 bytes Redo Buffers 6193152 bytes Database mounted. Database opened. SQL> show parameter undo_undo_retention SQL> show parameter undo_retention
数据库字符集验证：
