1.drop tuning task if task exists （删除之前的优化任务，如果存在的话）
sqlplus / as sysdba
exec DBMS_SQLTUNE.DROP_TUNING_TASK('zhangx_tune_taks'); <<ignore error if raise "taks does not exis "
2.create tuning task ,please replace sql_id 8gn0a9gxnc125 with yours.
创建一个新的sql优化任务，
DECLARE
tune_task VARCHAR2(30);
BEGIN
tune_task:=DBMS_SQLTUNE.CREATE_TUNING_TASK(sql_id=>'8gn0a9gxnc125',task_name=>'zhangx_tune_taks',time_limit => 600,description=>'ProvideSQLID');
END;
/
3.exec tuning task
BEGIN
DBMS_SQLTUNE.EXECUTE_TUNING_TASK( task_name => 'zhangx_tune_taks' );
END;
/
4.check tuning finding
set lines 999
set long 100000
set longchunksize 100000
select dbms_sqltune.report_tuning_task('zhangxiong_tune_taks') from dual;
