## Setup

Check if Automatic SQL Tuning Sets (ASTS) is activated (enabled) and get the last execution time of the automatic schedule:

	set lines 200
	col task_name for a22

	select * from dba_autotask_schedule_control where task_name = 'Auto STS Capture Task';
 
To enable:

	exec dbms_auto_task_admin.enable(client_name => 'Auto STS Capture Task', operation => NULL, window_name => NULL);

> No way to change the interval and maximum run time

To disable:

	exec dbms_auto_task_admin.disable(client_name => 'Auto STS Capture Task', operation => NULL, window_name => NULL);

To manually run the job:

	exec dbms_scheduler.run_job('ORA$_ATSK_AUTOSTS');

List last job executions:

	col ACTUAL_START_DATE for a45

	select ACTUAL_START_DATE,STATUS from dba_scheduler_job_run_details where JOB_NAME='ORA$_ATSK_AUTOSTS' 
	order by ACTUAL_START_DATE desc fetch first 10 rows only;

More statistics on the task job:

	WITH dsjrd AS
	(
	SELECT (TO_DATE('1','j')+run_duration-TO_DATE('1','j'))* 86400 duration_sec,
	       (TO_DATE('1','j')+cpu_used-TO_DATE('1','j'))* 86400 cpu_used_sec
	FROM dba_scheduler_job_run_details
	WHERE job_name = 'ORA$_ATSK_AUTOSTS'
	)
	SELECT MIN(duration_sec) ASTS_Min_Time_Sec,
	       MAX(duration_sec) ASTS_Max_Time_Sec,
	       AVG(duration_sec) ASTS_Average_Time_Sec,
	       AVG(cpu_used_sec) ASTS_Average_CPU_Sec
	FROM dsjrd;

How many SQL statements we have actually in the SYS_AUTO_STS SQL Tuning Set (STS):

	set lines 200
	col name for a15
	col description for a30
	col owner for a10

	select name, owner, description, created, last_modified, statement_count from dba_sqlset where name='SYS_AUTO_STS';
 
To purge all statements:

	exec dbms_sqlset.drop_sqlset(sqlset_name => 'SYS_AUTO_STS', sqlset_owner => 'SYS');

 How much space it takes in your SYSAUX tablesapce:

	col table_name for a30
	col table_size_mb for 999999.99
	col total_size_mb for 999999.99

	select
	  table_name,
	  round(sum(size_b) / 1024 / 1024, 3) as table_size_mb,
	  round(max(total_size_b) / 1024 / 1024, 3) as total_size_mb
	from
	  (
	    select
	      table_name,
	      size_b,
	      sum(size_b) over() as total_size_b
	      from
	      (
	        select
	          segment_name as table_name,
	          bytes as size_b
	        from dba_segments
	        where
	          segment_name not like '%WORKSPA%'
	          and owner = 'SYS'
	          and (segment_name like 'WRI%SQLSET%' or segment_name like 'WRH$_SQLTEXT')
	        union all
	        select
	          t.table_name,
	          bytes as size_b
	        from dba_segments s,
	          (select
	              table_name,
	              segment_name
	           from dba_lobs
	           where table_name in ('WRI$_SQLSET_PLAN_LINES', 'WRH$_SQLTEXT')
	           and owner = 'SYS'
	          ) t
	        where s.segment_name = t.segment_name
	      )
	  )
	group by table_name
	order by table_size_mb desc;

## Test case

	DROP TABLE test01 purge;
	CREATE TABLE test01(id NUMBER, descr VARCHAR(50)) TABLESPACE users;
	 
	DECLARE
	i NUMBER;
	nbrows NUMBER;
	BEGIN
	  i:=1;
	  nbrows:=50000;
	  LOOP
	    EXIT WHEN i>nbrows;
	    IF (i=1) THEN
	      INSERT INTO test01 VALUES(1,RPAD('A',49,'A'));
	    ELSE
	      INSERT INTO test01 VALUES(nbrows,RPAD('A',49,'A'));
	    END IF;
	    i:=i+1;
	  END LOOP;
	  COMMIT;
	END;
	/

	CREATE INDEX test01_idx_id ON test01(id);

	exec dbms_stats.gather_table_stats(ownname=>user, tabname=>'test01', method_opt=>'FOR ALL INDEXED COLUMNS SIZE AUTO');

No histogram will be calculated:

	col column_name for a20

	select column_name,num_distinct,density,num_nulls,num_buckets,sample_size,histogram  
	from user_tab_col_statistics  
	where table_name='TEST01'; 



	select  /*+ GATHER_PLAN_STATISTICS */ * FROM test01 WHERE id=1;

	        ID DESCR
	---------- --------------------------------------------------
	         1 AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

The optimize we will choose a full scan:

	SQL_ID  28stunrv2985c, child number 0
	-------------------------------------
	select  /*+ GATHER_PLAN_STATISTICS */ * FROM test01 WHERE id=1

	Plan hash value: 262542483

	-----------------------------------------------------------------------------------------------------------
	| Id  | Operation         | Name   | Starts | E-Rows |E-Bytes| Cost (%CPU)| A-Rows |   A-Time   | Buffers |
	-----------------------------------------------------------------------------------------------------------
	|   0 | SELECT STATEMENT  |        |      1 |        |       |   136 (100)|      1 |00:00:00.01 |     443 |
	|*  1 |  TABLE ACCESS FULL| TEST01 |      1 |  25000 |   732K|   136   (0)|      1 |00:00:00.01 |     443 |
	-----------------------------------------------------------------------------------------------------------


Wait for next Auto STS Capture Task schedule or run the job manually.
The SQL_ID will be captured bu ASTS:

	col SQLSET_NAME for a30
	col PARSING_SCHEMA_NAME for a30

	select SQLSET_NAME,PLAN_HASH_VALUE,PARSING_SCHEMA_NAME,BUFFER_GETS from DBA_SQLSET_STATEMENTS where SQL_ID='28stunrv2985c';

	SQLSET_NAME                    PLAN_HASH_VALUE PARSING_SCHEMA_NAME            BUFFER_GETS
	------------------------------ --------------- ------------------------------ -----------
	SYS_AUTO_STS                         262542483 RED                                    453

Gather the stats again:

	exec dbms_stats.gather_table_stats(ownname=>user, tabname=>'test01', method_opt=>'FOR ALL INDEXED COLUMNS SIZE AUTO');

Oracle learned from its mistake and will calulate histograms:

	COLUMN_NAME          NUM_DISTINCT    DENSITY  NUM_NULLS NUM_BUCKETS SAMPLE_SIZE HISTOGRAM
	-------------------- ------------ ---------- ---------- ----------- ----------- ---------------
	ID                              2     .00001          0           2       50000 FREQUENCY

Flush the shared pool and re-execute the query:

	alter system flush shared_pool;

	select  /*+ GATHER_PLAN_STATISTICS */ * FROM test01 WHERE id=1;

As expected, the index has been used:

	SQL_ID  28stunrv2985c, child number 0
	-------------------------------------
	select  /*+ GATHER_PLAN_STATISTICS */ * FROM test01 WHERE id=1

	Plan hash value: 4138272685

	------------------------------------------------------------------------------------------------------------------------------------
	| Id  | Operation                           | Name          | Starts | E-Rows |E-Bytes| Cost (%CPU)| A-Rows |   A-Time   | Buffers |
	------------------------------------------------------------------------------------------------------------------------------------
	|   0 | SELECT STATEMENT                    |               |      1 |        |       |     2 (100)|      1 |00:00:00.01 |       4 |
	|   1 |  TABLE ACCESS BY INDEX ROWID BATCHED| TEST01        |      1 |      1 |    30 |     2   (0)|      1 |00:00:00.01 |       4 |
	|*  2 |   INDEX RANGE SCAN                  | TEST01_IDX_ID |      1 |      1 |       |     1   (0)|      1 |00:00:00.01 |       3 |
	------------------------------------------------------------------------------------------------------------------------------------

Wait for next Auto STS Capture Task schedule and check if the SQL_ID is in with both executions.
> For me the manual execution does not add the 2-end plan to ASTS.

	select SQLSET_NAME,PLAN_HASH_VALUE,PARSING_SCHEMA_NAME,BUFFER_GETS from DBA_SQLSET_STATEMENTS where SQL_ID='28stunrv2985c';

	SQLSET_NAME                    PLAN_HASH_VALUE PARSING_SCHEMA_NAME            BUFFER_GETS
	------------------------------ --------------- ------------------------------ -----------
	SYS_AUTO_STS                         262542483 RED                                    453
	SYS_AUTO_STS                        4138272685 RED                                    203