Oracle - Performance Tuning SQL code using DBMS_SQLTUNE

The below write up gives a step by step approach to performance tune a query using the Oracle built in Package : DBMS_SQLTUNE 

Though this wont replace a manual performance tuning effort, it can get you started in the right direction or help you spot the obvious that you had always missed.

Please note this package required special licensing requirements to be used

STEP 1: Create a Tuning Task

DECLARE
DECLARE
  my_sqltext CLOB;
  task_name VARCHAR2(30);
BEGIN
  my_sqltext := 'SELECT DISTINCT PARENT_CUST_DOC_ID FROM APPS.XX_AR_EBL_CONS_HDR_HIST WHERE EXTRACT_BATCH_ID = 234';
  task_name := DBMS_SQLTUNE.CREATE_TUNING_TASK( sql_text => my_sqltext,
                                   user_name => 'APPS',
                                   scope => 'COMPREHENSIVE',
                                   time_limit => 60,
                                   task_name => 'sql_tuning_cons_ebill4');

END;

STEP 2: Execute the Task

begin
dbms_sqltune.execute_tuning_task ( 'sql_tuning_cons_ebill4');
end;

STEP 3: Check if the task has completed

SELECT task_name, status FROM dba_advisor_log WHERE task_name= 'sql_tuning_cons_ebill4';

STEP 4: Generate Report 

select dbms_sqltune.report_tuning_task('sql_tuning_cons_ebill4') from dual;

The suggestion below is to analyze the table and then create a index on extact_batch_id which gives a 98% benefit.

GENERAL INFORMATION SECTION
-------------------------------------------------------------------------------
Tuning Task Name                  : sql_tuning_cons_ebill4
Tuning Task Owner                 : APPS
Scope                             : COMPREHENSIVE
Time Limit(seconds)               : 60
Completion Status                 : COMPLETED
Started at                        : 07/16/2010 18:37:22
Completed at                      : 07/16/2010 18:37:22
Number of Statistic Findings      : 1
Number of Index Findings          : 1

-------------------------------------------------------------------------------
Schema Name: APPS
SQL ID     : dt7baa656pgxr
SQL Text   : SELECT DISTINCT PARENT_CUST_DOC_ID FROM
             APPS.XX_AR_EBL_CONS_HDR_HIST WHERE EXTRACT_BATCH_ID = 234

-------------------------------------------------------------------------------
FINDINGS SECTION (2 findings)
-------------------------------------------------------------------------------

1- Statistics Finding
---------------------
  Table "XXFIN"."XX_AR_EBL_CONS_HDR_HIST" and its indices were not analyzed.

  Recommendation
  --------------
  - Consider collecting optimizer statistics for this table and its indices.
    execute dbms_stats.gather_table_stats(ownname => 'XXFIN', tabname =>
            'XX_AR_EBL_CONS_HDR_HIST', estimate_percent =>
            DBMS_STATS.AUTO_SAMPLE_SIZE, method_opt => 'FOR ALL COLUMNS SIZE
            AUTO', cascade => TRUE);

  Rationale
  ---------
    The optimizer requires up-to-date statistics for the table and its indices
    in order to select a good execution plan.

2- Index Finding (see explain plans section below)
--------------------------------------------------
  The execution plan of this statement can be improved by creating one or more
  indices.

  Recommendation (estimated benefit: 98.06%)
  ------------------------------------------
  - Consider running the Access Advisor to improve the physical schema design
    or creating the recommended index.
    create index XXFIN.IDX$$_5D6710001 on
    XXFIN.XX_AR_EBL_CONS_HDR_HIST("EXTRACT_BATCH_ID");

  Rationale
  ---------
    Creating the recommended indices significantly improves the execution plan
    of this statement. However, it might be preferable to run "Access Advisor"
    using a representative SQL workload as opposed to a single statement. This
    will allow to get comprehensive index recommendations which takes into
    account index maintenance overhead and additional space consumption.

-------------------------------------------------------------------------------
EXPLAIN PLANS SECTION
-------------------------------------------------------------------------------

1- Original
-----------
Plan hash value: 3839049120

----------------------------------------------------------------------------------------------
| Id  | Operation          | Name                    | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT   |                         |     2 |    52 |   103   (1)| 00:00:02 |
|   1 |  HASH UNIQUE       |                         |     2 |    52 |   103   (1)| 00:00:02 |
|*  2 |   TABLE ACCESS FULL| XX_AR_EBL_CONS_HDR_HIST |     2 |    52 |   102   (0)| 00:00:02 |
----------------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   2 - filter("EXTRACT_BATCH_ID"=234)

2- Using New Indices
--------------------
Plan hash value: 3594741815

--------------------------------------------------------------------------------------------------------
| Id  | Operation                    | Name                    | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |                         |     1 |    26 |     2  (50)| 00:00:01 |
|   1 |  HASH UNIQUE                 |                         |     1 |    26 |     2  (50)| 00:00:01 |
|   2 |   TABLE ACCESS BY INDEX ROWID| XX_AR_EBL_CONS_HDR_HIST |     1 |    26 |     1   (0)| 00:00:01 |
|*  3 |    INDEX RANGE SCAN          | IDX$$_5D6710001         |     1 |       |     1   (0)| 00:00:01 |
--------------------------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   3 - access("EXTRACT_BATCH_ID"=234)

-------------------------------------------------------------------------------