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Oracle 11g中SPM指的是什么

发表于：2025-01-27 作者：千家信息网编辑

千家信息网最后更新 2025年01月27日，本篇文章为大家展示了Oracle 11g中SPM指的是什么，内容简明扼要并且容易理解，绝对能使你眼前一亮，通过这篇文章的详细介绍希望你能有所收获。前言我们知道,SQL语句的性能在很大程度上依赖于SQL

千家信息网最后更新 2025年01月27日Oracle 11g中SPM指的是什么

本篇文章为大家展示了Oracle 11g中SPM指的是什么，内容简明扼要并且容易理解，绝对能使你眼前一亮，通过这篇文章的详细介绍希望你能有所收获。

前言
我们知道,SQL语句的性能在很大程度上依赖于SQL语句的执行计划,如果SQL语句的执行计划发生变化,那么SQL语句的性能有可能发生很大的变化。影响SQL语句执行计划的因素很多,常见的有:

▪优化器版本的变化

▪统计信息的变化

▪优化器相关的各种参数的变化

▪对象定义的修改

▪添加、删除相关索引

▪修改了系统的设置

▪绑定变量的"窥视"功能

▪绑定变量的定义发生变化（比如类型或长度有变化）

▪启用了outline或SQL Profile等设置

11g前我们的处理方式

在Oracle 11g前，我们可以借助存储大纲(Stored Outline)和SQL Profile来帮助我们固定某个SQL语句的执行计划，防止由于执行计划的改变从而导致SQL性能的衰退。不过这些技术需要DBA人为的处理，比如存储大纲需要DBA手工创建，而对10g中提供的SQL Profile来说，则需要DBA手工应用才可以生效。

11g中，Oracle 提供了SPM

SPM就是Sql Plan Management,是Oracle自我管理（或者说自动性）发展的新功能。通过这个特性，Oracle自动去判断某个SQL的新的执行计划是否更加合理（成本更低），只有在新的执行计划比原来的执行计划更好的情况下，它才会被使用，从而有效的保护了执行计划的稳定性，进而保证了SQL语句的执行效率。

关于SPM的工作原理,本文不做详细的介绍,有兴趣的同志可以参阅相关的资料(网上类似的文章也不少)

执行计划管理实例测试

测试一:自动捕获的场景

Connected to Oracle Database 11g Enterprise Edition Release 11.1.0.6.0
Connected as study

SQL> create table test as select * from dba_objects;
Table created

SQL> exec DBMS_STATS.gather_table_stats(USER, 'TEST', cascade=>TRUE);
PL/SQL procedure successfully completed

SQL> select object_name from test where object_id=100;
OBJECT_NAME
----------------
FIXED_OBJ$

SQL> select object_name from test where object_id=100;
OBJECT_NAME
----------------
FIXED_OBJ$

尽管上面的查询语句执行了2次,但这个时候去查询dba_sql_plan_baseline的时候会发现,找不到我们需要的记录,因为这个时候optimizer_capture_sql_plan_baselines设置为false.禁止了自动捕获的功能.下面我将该参数设置为true,继续测试看看:

SQL> alter session set optimizer_capture_sql_plan_baselines=true;
Session altered

SQL> select object_name from test where object_id=100;

OBJECT_NAME
--------------------
FIXED_OBJ$

SQL> select object_name from test where object_id=100;

OBJECT_NAME
--------------------
FIXED_OBJ$

SQL> select signature,sql_handle,plan_name,origin,enabled,accepted,autopurge from dba_sql_plan_baselines;

SIGNATURE SQL_HANDLE PLAN_NAME ORIGIN ENABLED ACCEPTED AUTOPURGE
---------- --------------------------- ------------------------------ -------------- ------- -------- ---------
4.32736134 SYS_SQL_3c0de038050ab8f1 SYS_SQL_PLAN_050ab8f197bbe3d0 AUTO-CAPTURE YES YES YES

这个时候,我们再去查询dba_sql_plan_baseline的时候,就会发现该语句在plan history中记录了一个执行计划.

几个关键字段的说明

sql_handle：表示SQL语句的句柄

plan_name：表示该SQL语句执行计划的名字

origin：表示该执行计划是如何进入plan history的。AUTO-CAPTURE：优化器自动加入；MANUAL：DBA手工加入

enabled：表示是否被启用了。YES：启用 NO：禁用。如果某个执行计划为禁用，则优化器根本就不会考虑使用该执行计划

accepted：表示是否接受，也就是是否进入了plan baseline里，YES表示接受，NO表示不接受

autopurge：表示是否为定期自动删除,YES表示是，NO表示否。

fixed：当plan baseline中有多个执行计划时，表示优化器仅考虑这些被设置为FIXED的计划，从中选择一个最优的。

继续测试的旅程，新加一个index，再执行上面的SQL语句：

SQL> create index inx_test_object_id on test(object_id);
Index created

SQL> exec DBMS_STATS.gather_table_stats(USER, 'TEST', cascade=>TRUE);
PL/SQL procedure successfully completed

SQL> select object_name from test where object_id=100;

OBJECT_NAME
-----------------
FIXED_OBJ$

SQL> select signature,sql_handle,plan_name,origin,enabled,accepted,autopurge from dba_sql_plan_baselines;

SIGNATURE SQL_HANDLE PLAN_NAME ORIGIN ENABLED ACCEPTED AUTOPURGE
---------- -------------------------- ------------------------------ ------------- ------- -------- ---------
4.32736134 SYS_SQL_3c0de038050ab8f1 SYS_SQL_PLAN_050ab8f127b7cc01 AUTO-CAPTURE YES NO YES
4.32736134 SYS_SQL_3c0de038050ab8f1 SYS_SQL_PLAN_050ab8f197bbe3d0 AUTO-CAPTURE YES YES YES

SQL>

可以看到，dba_sql_plan_baselines视图里多了一个执行计划（上面灰色的），不过该执行计划的accepted为NO，表示还没有进入到plan baseline里，而是进入了plan history中。

如果想让该计划进入到plan baseline中，我们可以借助dbms_spm来完成：

       Connected to Oracle Database 11g Enterprise Edition Release 11.1.0.6.0        Connected as study              SQL>        SQL> set serveroutput on long 100000       SQL> declare         2     report clob;         3  begin         4     report := dbms_spm.evolve_sql_plan_baseline(sql_handle => 'SYS_SQL_3c0de038050ab8f1',         5                                                 plan_name => 'SYS_SQL_PLAN_050ab8f127b7cc01');         6     dbms_output.put_line(report);         7  end;         8  /                     -------------------------------------------------------------------------------                               Evolve SQL Plan Baseline Report       -------------------------------------------------------------------------------              Inputs:       -------         SQL_HANDLE = SYS_SQL_3c0de038050ab8f1         PLAN_NAME  = SYS_SQL_PLAN_050ab8f127b7cc01         TIME_LIMIT = DBMS_SPM.AUTO_LIMIT         VERIFY     = YES         COMMIT     = YES              Plan: SYS_SQL_PLAN_050ab8f127b7cc01       -----------------------------------         Plan was verified: Time used .062 seconds.         Passed performance criterion: Compound improvement ratio >= 337.17.         Plan was changed to an accepted plan.                                    Baseline Plan      Test Plan     Improv. Ratio                             -------------      ---------     -------------         Execution Status:        COMPLETE       COMPLETE         Rows Processed:                 1              1         Elapsed Time(ms):              13              0         CPU Time(ms):                  15              0         Buffer Gets:                 1010              3            336.67         Disk Reads:                     0              0         Direct Writes:                  0              0         Fetches:                        0              0         Executions:                     1              1              -------------------------------------------------------------------------------                                        Report Summary       -------------------------------------------------------------------------------       Number of SQL plan baselines verified: 1.       Number of SQL plan baselines evolved: 1.                     PL/SQL procedure successfully completed              SQL>

再看一下dba_sql_plan_baselines

SQL> select signature,sql_handle,plan_name,origin,enabled,accepted,autopurge from dba_sql_plan_baselines;

SIGNATURE SQL_HANDLE PLAN_NAME ORIGIN ENABLED ACCEPTED AUTOPURGE
---------- -------------------------- ------------------------------ ------------- ------- -------- ---------
4.32736134 SYS_SQL_3c0de038050ab8f1 SYS_SQL_PLAN_050ab8f197bbe3d0 AUTO-CAPTURE YES YES YES
4.32736134 SYS_SQL_3c0de038050ab8f1 SYS_SQL_PLAN_050ab8f127b7cc01 AUTO-CAPTURE YES YES YES
SQL>

咱们分别看一下这两个执行计划的详细信息：

SQL> select * from table(DBMS_XPLAN.display_sql_plan_baseline(plan_name=>'SYS_SQL_PLAN_050ab8f127b7cc01')); PLAN_TABLE_OUTPUT -------------------------------------------------------------------------------- SQL handle: SYS_SQL_3c0de038050ab8f1 SQL text: select object_name from test where object_id=100 -------------------------------------------------------------------------------- Plan name: SYS_SQL_PLAN_050ab8f127b7cc01 Enabled: YES Fixed: NO Accepted: YES Origin: AUTO-CAPTURE -------------------------------------------------------------------------------- Plan hash value: 2422726699 -------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost -------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | 30 | 2 | 1 | TABLE ACCESS BY INDEX ROWID| TEST | 1 | 30 | 2 |* 2 | INDEX RANGE SCAN | INX_TEST_OBJECT_ID | 1 | | 1 -------------------------------------------------------------------------------- PLAN_TABLE_OUTPUT -------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - access("OBJECT_ID"=100) 25 rows selected SQL> SQL> select * from table(DBMS_XPLAN.display_sql_plan_baseline(plan_name=>'SYS_SQL_PLAN_050ab8f197bbe3d0')); PLAN_TABLE_OUTPUT -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- SQL handle: SYS_SQL_3c0de038050ab8f1 SQL text: select object_name from test where object_id=100 -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- Plan name: SYS_SQL_PLAN_050ab8f197bbe3d0 Enabled: YES Fixed: NO Accepted: YES Origin: AUTO-CAPTURE -------------------------------------------------------------------------------- Plan hash value: 1357081020 -------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | -------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | 30 | 282 (1)| 00:00:04 | |* 1 | TABLE ACCESS FULL| TEST | 1 | 30 | 282 (1)| 00:00:04 | -------------------------------------------------------------------------- PLAN_TABLE_OUTPUT -------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 1 - filter("OBJECT_ID"=100) 24 rows selected SQL>

在看看这个SQL执行时到底选择了那个baseline:

SQL> conn study/study 已连接。 SQL> set autotrace trace SQL> select object_name from test where object_id=100; 执行计划 ---------------------------------------------------------- Plan hash value: 2422726699 -------------------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost(%CPU)| Time | -------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | 30 | 2 (0)| 00:00:01 | | 1 | TABLE ACCESS BY INDEX ROWID| TEST | 1 | 30 | 2 (0)| 00:00:01 | |* 2 | INDEX RANGE SCAN | INX_TEST_OBJECT_ID | 1 | | 1 (0)| 00:00:01 | -------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - access("OBJECT_ID"=100) Note ----- - SQL plan baseline "SYS_SQL_PLAN_050ab8f127b7cc01" used for this statement SQL>　

下面再熟悉一下手工删除plan baseline里的执行计划，同样可以借助dbms_spm来完成。下面的DEMO把上面baseline里走full table scan的执行计划清除：

SQL> var ret number
SQL> exec :ret:=dbms_spm.drop_sql_plan_baseline(sql_handle => 'SYS_SQL_3c0de038050ab8f1',
plan_name => 'SYS_SQL_PLAN_050ab8f197bbe3d0');

PL/SQL procedure successfully completed
ret
---------
1

SQL>
SQL> select signature,sql_handle,plan_name,origin,enabled,accepted,autopurge from dba_sql_plan_baselines;

SIGNATURE SQL_HANDLE PLAN_NAME ORIGIN ENABLED ACCEPTED AUTOPURGE
---------- ------------------------ ------------------------------ -------------- ------- -------- ---------
4.32736134 SYS_SQL_3c0de038050ab8f1 SYS_SQL_PLAN_050ab8f127b7cc01 AUTO-CAPTURE YES YES YES

SQL>

测试二:手动捕获的场景

       Connected to Oracle Database 11g Enterprise Edition Release 11.1.0.6.0        Connected as study              SQL> select sql_text,sql_id from v$sql where sql_text like '%select object_name from test where%';              SQL_TEXT                                              SQL_ID       ----------------------------------------------------- -------------       select object_name from test where object_id=100      7j7jc706upva2                     SQL>        SQL> set serveroutput on       SQL> declare         2    l_plans_loaded  PLS_INTEGER;         3  begin         4    l_plans_loaded := DBMS_SPM.load_plans_from_cursor_cache(         5      sql_id => '7j7jc706upva2');         6           7    DBMS_OUTPUT.put_line('Plans Loaded: ' || l_plans_loaded);         8  END;         9  /              Plans Loaded: 1              PL/SQL procedure successfully completed              SQL>        SQL> select signature,sql_handle,plan_name,origin,enabled,accepted,autopurge         2  from dba_sql_plan_baselines;               SIGNATURE SQL_HANDLE                PLAN_NAME                      ORIGIN      ENABLED ACCEPTED AUTOPURGE       ---------- ------------------------- ------------------------------ ----------- ------- -------- ---------       4.32736134 SYS_SQL_3c0de038050ab8f1  SYS_SQL_PLAN_050ab8f127b7cc01  MANUAL-LOAD YES     YES      YES              SQL>

上述内容就是Oracle 11g中SPM指的是什么，你们学到知识或技能了吗？如果还想学到更多技能或者丰富自己的知识储备，欢迎关注行业资讯频道。

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