SQL> select * from nls_database_parameters where parameter='NLS_CHARACTERSET';
SQL> shutdown immediate
SQL> startup mount
SQL> alter system enable restricted session;
SQL> show parameter job_queue_processes;
SQL> alter system set job_queue_processes=0;
SQL> alter database open;
SQL> alter database character set internal_use ZHS16GBK;
SQL> select * from nls_database_parameters where parameter='NLS_CHARACTERSET';
SQL> shutdown immediate
SQL> startup mount
SQL> alter system set job_queue_processes=10;
SQL> alter database open;