When we run SQL tuning advisor against a SQL statement or sql_id, it provides tuning recommendations that can be done that query to improve performance. It might give suggestion to create few indexes or accepting a SQL profile.

Diagnostic and Tuning license is required to use this feature

In this below tutorial we will explain how to run sql tuning advisor against sql_Id.

Suppose the sql id is – 87s8z2zzpsg88

1. Create Tuning Task

DECLARE
  l_sql_tune_task_id  VARCHAR2(100);
BEGIN
  l_sql_tune_task_id := DBMS_SQLTUNE.create_tuning_task (
                          sql_id      => '87s8z2zzpsg88',
                          scope       => DBMS_SQLTUNE.scope_comprehensive,
                          time_limit  => 500,
                          task_name   => '87s8z2zzpsg88_tuning_task11',
                          description => 'Tuning task1 for statement 87s8z2zzpsg88');
  DBMS_OUTPUT.put_line('l_sql_tune_task_id: ' || l_sql_tune_task_id);
END;
/

2. Execute Tuning task:

EXEC DBMS_SQLTUNE.execute_tuning_task(task_name => '87s8z2zzpsg88_tuning_task11'); 

3. Get the Tuning advisor report.

 
set long 65536
set longchunksize 65536
set linesize 100
select dbms_sqltune.report_tuning_task('87s8z2zzpsg88_tuning_task11') from dual;

 

4. Get list of tuning task present in database:

We can get the list of tuning tasks present in database from DBA_ADVISOR_LOG

SELECT TASK_NAME, STATUS FROM DBA_ADVISOR_LOG WHERE TASK_NAME ;

5. Drop a tuning task:

execute dbms_sqltune.drop_tuning_task('87s8z2zzpsg88_tuning_task11');

 

What if the sql_id is not present in the cursor , but present in AWR snap?

SQL_ID =24pzs2d6a6b13

First we need to find the begin snap and end snap of the sql_id.

select a.instance_number inst_id, a.snap_id,a.plan_hash_value, to_char(begin_interval_time,'dd-mon-yy hh24:mi') btime, abs(extract(minute from (end_interval_time-begin_interval_time)) + extract(hour from (end_interval_time-begin_interval_time))*60 + extract(day from (end_interval_time-begin_interval_time))*24*60) minutes,
executions_delta executions, round(ELAPSED_TIME_delta/1000000/greatest(executions_delta,1),4) "avg duration (sec)" from dba_hist_SQLSTAT a, dba_hist_snapshot b
where sql_id='&sql_id' and a.snap_id=b.snap_id
and a.instance_number=b.instance_number
order by snap_id desc, a.instance_number;

From here we can get the begin snap and end snap of the sql_id.

begin_snap -> 235
end_snap -> 240

1. Create the tuning task:

DECLARE
  l_sql_tune_task_id  VARCHAR2(100);
BEGIN
  l_sql_tune_task_id := DBMS_SQLTUNE.create_tuning_task (
                          begin_snap  => 235,
                          end_snap    => 240,
                          sql_id      => '24pzs2d6a6b13',
                          scope       => DBMS_SQLTUNE.scope_comprehensive,
                          time_limit  => 60,
                          task_name   => '24pzs2d6a6b13_AWR_tuning_task',
                          description => 'Tuning task for statement 24pzs2d6a6b13  in AWR');
  DBMS_OUTPUT.put_line('l_sql_tune_task_id: ' || l_sql_tune_task_id);
END;
/

2. Execute the tuning task:

EXEC DBMS_SQLTUNE.execute_tuning_task(task_name => '24pzs2d6a6b13_AWR_tuning_task');

3. Get the tuning task recommendation report

SET LONG 10000000;
SET PAGESIZE 100000000

SET LINESIZE 200
SELECT DBMS_SQLTUNE.report_tuning_task('24pzs2d6a6b13_AWR_tuning_task') AS recommendations FROM dual;
SET PAGESIZE 24

 

SEE ALSO – COLLECTION OF USEFUL DATABASE MONITORING SCRIPT