Oracle SQL Tunning Advisor
-The SQL Tuning Advisor takes one or more SQL statements as an input and invokes the Automatic Tuning Optimizer to perform SQL tuning on the statements.
-The output of the SQL Tuning Advisor is in the form of an recommendations, along with a rationale for each recommendation and its expected benefit.The recommendation relates to collection of statistics on objects, creation of new indexes, restructuring of the SQL statement, or creation of a SQL profile. You can choose to accept the recommendation to complete the tuning of the SQL statements.
-You can also run the SQL Tuning Advisor selectively on a single or a set of SQL statements that have been identified as problematic.
-We can find the problematic SQL_ID from v$session you would like to analyze. Usually the AWR has the top SQL_IDs column.
In order to access the SQL tuning advisor API, a user must be granted the ADVISOR privilege:
How To Run SQL Tuning Advisor For A Sql_id
Example: SQL_ID=4gk55ct4mnmh3
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 => '4gk55ct4mnmh3',
scope => DBMS_SQLTUNE.scope_comprehensive,
time_limit => 500,
task_name => '4gk55ct4mnmh3_tuning_task11',
description => 'Tuning task1 for statement 4gk55ct4mnmh3');
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 => '4gk55ct4mnmh3_tuning_task11');
3. Get the Tuning advisor report.
set long 65536
set longchunksize 65536
set linesize 100
select dbms_sqltune.report_tuning_task('4gk55ct4mnmh3_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='4gk55ct4mnmh3_tuning_task11'; ----> task_name
5. Drop a tuning task:
execute dbms_sqltune.drop_tuning_task('4gk55ct4mnmh3_tuning_task11');
What if the sql_id is not present in the cursor, but present in AWR snap?
SQL_ID =4gk55ct4mnmh3
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 => '4gk55ct4mnmh3',
scope => DBMS_SQLTUNE.scope_comprehensive,
time_limit => 60,
task_name => '4gk55ct4mnmh3_AWR_tuning_task',
description => 'Tuning task for statement 4gk55ct4mnmh3 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 => '4gk55ct4mnmh3_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('4gk55ct4mnmh3_AWR_tuning_task') AS recommendations FROM dual;
SET PAGESIZE 24
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