$ sqlplus "/as sysdba"
SQL> conn /as sysdba;
SQL> shutdown immediate;
SQL> startup mount;
SQL> ALTER SYSTEM ENABLE RESTRICTED SESSION;
SQL> ALTER SYSTEM SET JOB_QUEUE_PROCESSES=0;
SQL> ALTER SYSTEM SET AQ_TM_PROCESSES=0;
SQL> alter database open;
SQL> alter database character set INTERNAL_USE UTF8;
SQL> shutdown immediate;
SQL> startup;
SQL> exit;