11g r2中的SPM的使用

参考文档： Oracle database 11gr2 性能调整与优化

1 启用捕获并多次运行sql语句，以便于SPM判断语句是否可重复，然后关闭捕获

alter session set optimizer_capture_sql_plan_baselines=true;
select * /* ebk1 */ from scott.emp where job='PRESIDENT';
select * /* ebk1 */ from scott.emp where job='PRESIDENT';
alter session set optimizer_capture_sql_plan_baselines=false;

2 查询dba_sql_plan_baselines,确定SQL语句在SPM中的状态

select plan_name,sql_handle,enabled,accepted,fixed,module,sql_text from dba_sql_plan_baselines;

3 增加索引以改变环境，并再次运行该SQL语句

create index idx_job on scott.emp(job);
alter session set optimizer_capture_sql_plan_baselines=true;
select * /* ebk1 */ from scott.emp where job='PRESIDENT';
select * /* ebk1 */ from scott.emp where job='PRESIDENT';
alter session set optimizer_capture_sql_plan_baselines=false;

4 查询dba_sql_plan_baselines,确定SQL语句在SPM中的状态

select plan_name,sql_handle,enabled,accepted,fixed,module,sql_text from dba_sql_plan_baselines;

设置optimizer_use_sql_plan_baseline为false，并允许优化器选择计划
然后设置额optimizer_use_sql_plan_baseline为true，强制优化器在计划基线中仅选择一个已接受的计划

在第一种情况下，优化器选择了使用索引的计划。但是在第二种情况下，没有使用。因为这是未被接受的计划。

alter system set optimizer_use_sql_plan_baselines=true;
explain plan for
select * /* ebk1 */ from scott.emp where job='PRESIDENT';

select * from table(dbms_xplan.display(null,null,'basic'))


SYS@test>select * from table(dbms_xplan.display(null,null,'basic'));

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Plan hash value: 3956160932

----------------------------------
| Id  | Operation	  | Name |
----------------------------------
|   0 | SELECT STATEMENT  |	 |
|   1 |  TABLE ACCESS FULL| EMP  |
----------------------------------

8 rows selected.


alter system set optimizer_use_sql_plan_baselines=false;
explain plan for
select * /* ebk1 */ from scott.emp where job='PRESIDENT';

select * from table(dbms_xplan.display(null,null,'basic'))


SYS@test>select * from table(dbms_xplan.display(null,null,'basic'));

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Plan hash value: 3894156048

-----------------------------------------------
| Id  | Operation		    | Name    |
-----------------------------------------------
|   0 | SELECT STATEMENT	    |	      |
|   1 |  TABLE ACCESS BY INDEX ROWID| EMP     |
|   2 |   INDEX RANGE SCAN	    | IDX_JOB |
-----------------------------------------------

9 rows selected.

接下来，改善SQL计划，允许accepted状态为NO的计划变成yes 。

set serveroutput on
set long 10000
declare 
   report clob;
begin 
   report:=dbms_spm.evolve_sql_plan_baseline(
   sql_handle=>'SQL_5351f0dc28458c6a');
   dbms_output.put_line(report);
end;
/


SYS@test>set serveroutput on
set long 10000
declare 
   report clob;
begin 
   report:=dbms_spm.evolve_sql_plan_baseline(
   sql_handle=>'SQL_5351f0dc28458c6a');
   dbms_output.put_line(report);
end;
/SYS@test>SYS@test>  2    3    4    5    6    7    8  

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

			Evolve SQL Plan Baseline
Report
-------------------------------------------------------------------------
------

Inputs:
-------
  SQL_HANDLE = SQL_5351f0dc28458c6a
  PLAN_NAME  = 

TIME_LIMIT = DBMS_SPM.AUTO_LIMIT
  VERIFY     = YES
  COMMIT     = YES

Plan:
SQL_PLAN_56nghvhn4b33aa2f1f054
------------------------------------
  Plan was
verified: Time used 0 seconds.
  Plan passed performance criterion: 3 times
better than baseline plan.
  Plan was changed to an accepted plan.


Baseline Plan	   Test Plan	   Stats Ratio

-------------	   ---------	   -----------
  Execution Status:
COMPLETE       COMPLETE
  Rows Processed:			1
1
  Elapsed Time(ms):		     .011	    .008	      1.38

CPU Time(ms):			      0 	     0
  Buffer Gets:
6	       2		 3
  Physical Read Requests:		0
0
  Physical Write Requests:		0	       0
  Physical Read
Bytes:			0	       0
  Physical Write Bytes:
0	       0
  Executions:				1
1

-----------------------------------------------------------------------------
--
				 Report
Summary
------------------------------------------------------------------------
-------
Number of plans verified: 1
Number of plans accepted: 1


PL/SQL procedure successfully completed.

使用语句，或者EM查看，这个语句已经变成接受的了

这个时候，如果optimizer_use_sql_plan_baseline 为true，运行sql就会使用新的已接受的计划，因为
他的性能比其他已接受的计划好

alter system set optimizer_use_sql_plan_baselines=true;
explain plan for
select * /* ebk1 */ from scott.emp where job='PRESIDENT';

select * from table(dbms_xplan.display(null,null,'basic'))


SYS@test>explain plan for
select * /* ebk1 */ from scott.emp where job='PRESIDENT';  2  

Explained.

SYS@test>select * from table(dbms_xplan.display(null,null,'basic'));

PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 3894156048

-----------------------------------------------
| Id  | Operation		    | Name    |
-----------------------------------------------
|   0 | SELECT STATEMENT	    |	      |
|   1 |  TABLE ACCESS BY INDEX ROWID| EMP     |
|   2 |   INDEX RANGE SCAN	    | IDX_JOB |
-----------------------------------------------

9 rows selected.

SYS@test>

使用固定的SQL执行计划

declare 
l_plans_altered PLS_INTEGER;
begin
l_plans_altered :=dbms_spm.alter_sql_plan_baseline(
sql_handle=>'SQL_5351f0dc28458c6a',
plan_name=> null,
attribute_name=> 'fixed',
attribute_value=>'YES');
end;

再次查询，已经固定。或者在EM上查询

select plan_name,sql_handle,enabled,accepted,fixed,module,sql_text from dba_sql_plan_baselines;

删除计划：

set serveroutput on
declare
l_plan_dropped pls_integer;
begin
l_plan_dropped:=dbms_spm.drop_sql_plan_baseline(
sql_handle=>'SQL_5351f0dc28458c6a',
plan_name=>null);
end;

执行完毕后，在EM上看，看不到了

END。

补充，其实，这个知识点，是11gr2 OCM考试里面的一道题目。考试的时候，没有这个这么复杂，直接在EM上操作，很方便。也很迅速就完毕了。但是知道原理，还是好一些。