12.2 新功能优化器统计顾问(Optimizer Statistics Advisor)及常见问题

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文章目录

【12.2 新功能】优化器统计顾问(Optimizer Statistics Advisor)及常见问题

关键字Keyword

Optimizer Statistics Advisor,统计信息 ,ORA-20001 , ORA-00932 ,12.2.0.1

优化器统计顾问概述

对于Oracle的CBO优化器而言,统计信息是其最重要的组成部分。
因此,Oracle在统计信息的准确性方面不断地进行优化和加强。
从12.2版本开始,Oracle推出了优化器统计顾问(Optimizer Statistics Advisor),
根据事先定义的规则,定期执行,提供给用户参考的统计信息收集相关的建议。

参考:

Home/Database/Oracle/Oracle Database/Release 12.2
SQL Tuning Guide
https://docs.oracle.com/en/database/oracle/oracle-database/12.2/tgsql/optimizer-statistics-advisor.html#GUID-054F4B76-DD57-46EE-98EA-0FF04F49D1B3
>18 Analyzing Statistics Using Optimizer Statistics Advisor

Optimizer Statistics Advisor In 12.2 (Quick Overview) (Doc ID 2259398.1)
12c Release 2 New Feature : Statistics Advisor (Walk-Through) (Doc ID 2360311.1)
AUTO_STATS_ADVISOR_TASK Running Outside of Maintenance Window (Doc ID 2387110.1)

统计信息收集相关内容:

数据库自动维护任务介绍
数据库自动维护任务介绍(二)
自动统计信息收集Automatic Optimizer Statistics Collection
自动段指导Automatic Segment Advisor

在12.2.0.1以后的版本上运行该功能时,遇到问题的报告很多,但是Oracle也在不断地修正着相关地问题,所以保持数据库为最新版本通常是一个最佳的选择。

常见问题和解决方法:

问题1:ORA-12012, ORA-20001等错误

由于12.2.0.1等版本上的设计不足(Bug) 等,可能会在告警日志(alert log)或者JOB跟踪日志中,发现ORA-12012, ORA-20001等错误。

例:

>ORA-12012: error on auto execute of job "SYS"."ORA$AT_OS_OPT_SY_nn"
>ORA-20001: Statistics Advisor: Invalid Task Name For the current user
>ORA-06512: at "SYS.DBMS_STATS", line 46861
>ORA-06512: at "SYS.DBMS_STATS_ADVISOR", line 734
>ORA-06512: at "SYS.DBMS_STATS_INTERNAL", line 19930
>ORA-06512: at "SYS.DBMS_STATS_INTERNAL", line 21934
>ORA-06512: at "SYS.DBMS_STATS", line 46851

可以参考如下方法尝试解决。

1.通过dbms_stats.init_package()程序包,重新创建优化器统计顾问任务。

例:
EXEC dbms_stats.init_package();
  1. 首先看看这个bug 27983174和27774706是否被修复,如果存在则建议打上补丁或打上最新的RU.
    如果没有被修复,可向官方技术支持申请Patch 27983174 和Patch 27774706 补丁并应用。

  2. 应用Patch 27774706 补丁后,执行如下操作:

$ sqlplus / as sysdba
drop table WRI$_ADV_DEFINITIONS;
@?/rdbms/admin/catadvtb.sql
@?/rdbms/admin/utlrp.sql
execute dbms_advisor.setup_repository;
EXEC dbms_stats.init_package();

4.如果应用Patch 27774706 补丁过程中出错的话,试着执行如下命令手动更新状态。

UPDATE dba_registry_sqlpatch
SET status = 'SUCCESS', action_time = SYSTIMESTAMP
WHERE patch_id = 27774706 and status='WITH ERRORS' and rownum=1;
commit;

很多问题会在19c以后的版本进行修复,所以有可能的话注意保持版本的更新。

参考:

Recurring ORA-12012, ORA-20001, ORA-06512 In Container Database (Doc
ID 2420581.1) 12.2.0.0.2 Automatic Statistics Advisor Job Errors with
Statistics Fatal Error (Doc ID 2448436.1) Version 12.2.0.1 to
18.3.0.0.0 ORA-12012 Error on auto execute of job “SYS”."ORA$AT_OS_OPT_SY_ in 12.2.0 Database version or higher
release (like 18c) (Doc ID 2127675.1) Version 12.2.0.1 and later

问题2:SYSAUX表空间增长过快

由于优化器统计顾问的执行,SYSAUX表空间增长过快,导致可用表空间不足。

特征:
V S Y S A U X O C C U P A N T S 中 , S M / A D V I S O R 占 据 大 量 空 间 D B A S E G M E N T S 中 , W R I SYSAUX_OCCUPANTS中,SM/ADVISOR占据大量空间 DBA_SEGMENTS中,WRI SYSAUXOCCUPANTSSM/ADVISORDBASEGMENTSWRI_ADV_OBJECTS占据大量空间

解决方法:

  1. 尝试删除Statistics Advisor 任务(AUTO_STATS_ADVISOR_TASK),然后重建。

    具体删除方法例:

connect / as sysdba
--1.1 删除Statistics Advisor 任务
DECLARE
v_tname VARCHAR2(32767);
BEGIN
v_tname := 'AUTO_STATS_ADVISOR_TASK';
DBMS_STATS.DROP_ADVISOR_TASK(v_tname);
END;
/

--1.2 删除任务之后,重组表和所有索引
SQL> ALTER TABLE WRI$_ADV_OBJECTS MOVE;
SQL> ALTER INDEX WRI$_ADV_OBJECTS_IDX_01 REBUILD;
SQL> ALTER INDEX WRI$_ADV_OBJECTS_PK REBUILD;

注:如果在删除过程中,发生ORA-20001等错误的话,可以执行下面的方法重建AUTO_STATS_ADVISOR_TASK来解决,
    然后再执行上面的删除方法,最终达到删除Statistics Advisor 任务(AUTO_STATS_ADVISOR_TASK)的目的。

    SQL> connect / as sysdba
    SQL> EXEC DBMS_STATS.INIT_PACKAGE();

2. 缩短任务执行历史的保存时间

– 确认当前设定的保持期间
select task_name, parameter_name, parameter_value FROM DBA_ADVISOR_PARAMETERS
where task_name=‘AUTO_STATS_ADVISOR_TASK’ and PARAMETER_NAME like ‘%EXPIRE%’;

-- 修改设定的保持期间
可以通过下面的命令,将EXECUTION_DAYS_TO_EXPIRE修改为10天,即执行历史数据的保存时间为10天:

connect /as sysdba
BEGIN
 DBMS_SQLTUNE.SET_TUNING_TASK_PARAMETER (
  task_name => 'AUTO_STATS_ADVISOR_TASK'
 , parameter => 'EXECUTION_DAYS_TO_EXPIRE'
 , value => 10
);
END;
/

参考:

How To Set DAYS_TO_EXPIRE and EXECUTION_DAYS_TO_EXPIRE of Automatic Statistics Advisor Task (Doc ID 2544788.1)

注:未来版本中,可以通过如下方法禁用Statistics Advisor 任务。
    现阶段(2020/1)无法禁用这个任务。
    
DECLARE
filter1 CLOB;
BEGIN
filter1 := DBMS_STATS.CONFIGURE_ADVISOR_RULE_FILTER('AUTO_STATS_ADVISOR_TASK',NULL,NULL,'DISABLE');
END;
/

参考:

升级DB到12.2.0.1版本之后,由于统计信息顾问导致SYSAUX 过快增长 (Doc ID 2440139.1) SYSAUX
Tablespace Grows Rapidly After Upgrading Database to 12.2.0.1 Due To
Statistics Advisor (Doc ID 2305512.1)

3. 12.2.0.1版本由于Bug 26764561的影响,即使EXECUTION_DAYS_TO_EXPIRE设成10天后,优化器统计顾问相关段依然不断增加。 
   所以首先看看这个bug是否被修复,如果存在则建议打上补丁或打上最新的RU。

参考:

AUTO_STATS_ADVISOR_TASK Not Purging Even Though Setting EXECUTION_DAYS_TO_EXPIRE (Doc ID 2615851.1)

Bug 26764561(Doc ID 26764561.8)

  ※注意打补丁后的Postinstallation内容

■ 关于EXECUTION_DAYS_TO_EXPIRE的默认值:

ver<=18.3
    SQL> EXEC DBMS_STATS.INIT_PACKAGE();
    PL/SQL procedure successfully completed.

    SQL> SELECT parameter_name, parameter_value FROM DBA_ADVISOR_PARAMETERS
      WHERE task_name='AUTO_STATS_ADVISOR_TASK'
      and PARAMETER_NAME IN 'EXECUTION_DAYS_TO_EXPIRE';
      2    3
    PARAMETER_NAME
    --------------------------------------------------------------------------------
    PARAMETER_VALUE
    --------------------------------------------------------------------------------
    EXECUTION_DAYS_TO_EXPIRE
    UNLIMITED

Version 19.3.0.0.0 &18.5 (Bug 27983174修复后)

    SQL> SELECT parameter_name, parameter_value FROM DBA_ADVISOR_PARAMETERS
              WHERE task_name='AUTO_STATS_ADVISOR_TASK'
              and PARAMETER_NAME IN 'EXECUTION_DAYS_TO_EXPIRE';  2    3
    PARAMETER_NAME
    --------------------------------------------------------------------------------
    PARAMETER_VALUE
    --------------------------------------------------------------------------------
    EXECUTION_DAYS_TO_EXPIRE
    30

问题3:关于在多租户环境中 CDB/PDB的设置问题

对于多租户环境中,CDB/PDB的设置相对独立,互相不影响。

■EXECUTION_DAYS_TO_EXPIRE的CDB/PDB设置测试:

    ---CDB側
    SQL> conn / as sysdba
    Connected.
    SQL> SELECT parameter_name, parameter_value FROM DBA_ADVISOR_PARAMETERS
                      WHERE task_name='AUTO_STATS_ADVISOR_TASK'
                      and PARAMETER_NAME IN 'EXECUTION_DAYS_TO_EXPIRE';  2    3


    PARAMETER_NAME
    --------------------------------------------------------------------------------
    PARAMETER_VALUE
    --------------------------------------------------------------------------------
    EXECUTION_DAYS_TO_EXPIRE
    UNLIMITED




    SQL> show pdbs


        CON_ID CON_NAME                       OPEN MODE  RESTRICTED
    ---------- ------------------------------ ---------- ----------
             2 PDB$SEED                       READ ONLY  NO
             3 PDB1                           READ WRITE NO
    SQL>
    BEGIN
     DBMS_SQLTUNE.SET_TUNING_TASK_PARAMETER (
      task_name => 'AUTO_STATS_ADVISOR_TASK'
    , parameter => 'EXECUTION_DAYS_TO_EXPIRE'
    , value => 30
    );
    END;
    /
    SQL>   2    3    4    5    6    7    8
    PL/SQL procedure successfully completed.


    SQL> SELECT parameter_name, parameter_value FROM DBA_ADVISOR_PARAMETERS
                      WHERE task_name='AUTO_STATS_ADVISOR_TASK'
                      and PARAMETER_NAME IN 'EXECUTION_DAYS_TO_EXPIRE';   2    3


    PARAMETER_NAME
    --------------------------------------------------------------------------------
    PARAMETER_VALUE
    --------------------------------------------------------------------------------
    EXECUTION_DAYS_TO_EXPIRE
    30

   ---PDB側
    SQL> alter session set container=pdb1;
    Session altered.
   SQL> SELECT parameter_name, parameter_value FROM DBA_ADVISOR_PARAMETERS
                      WHERE task_name='AUTO_STATS_ADVISOR_TASK'
                      and PARAMETER_NAME IN 'EXECUTION_DAYS_TO_EXPIRE';  
    PARAMETER_NAME
    --------------------------------------------------------------------------------
    PARAMETER_VALUE
    --------------------------------------------------------------------------------
    EXECUTION_DAYS_TO_EXPIRE
    UNLIMITED


    SQL> show pdbs
        CON_ID CON_NAME                       OPEN MODE  RESTRICTED
    ---------- ------------------------------ ---------- ----------
             3 PDB1                           READ WRITE NO
    SQL>

■PDB/CDB的JOB关联性的测试:

SQL> conn / as sysdba
Connected.
SQL> select name, ctime, how_created,OWNER_NAME from sys.wri$_adv_tasks
where name in (‘AUTO_STATS_ADVISOR_TASK’,‘INDIVIDUAL_STATS_ADVISOR_TASK’); 2
AUTO_STATS_ADVISOR_TASK 25-SEP-19 CMD SYS

SQL> DECLARE
v_tname VARCHAR2(32767);
BEGIN
v_tname := ‘AUTO_STATS_ADVISOR_TASK’;
DBMS_STATS.DROP_ADVISOR_TASK(v_tname);
END;
/ 2 3 4 5 6 7
PL/SQL procedure successfully completed.

SQL> select name, ctime, how_created,OWNER_NAME from sys.wri a d v t a s k s w h e r e n a m e i n ( ′ A U T O S T A T S A D V I S O R T A S K ′ , ′ I N D I V I D U A L S T A T S A D V I S O R T A S K ′ ) ; 2 n o r o w s s e l e c t e d S Q L > s h o w p d b s 2 P D B _adv_tasks where name in ('AUTO_STATS_ADVISOR_TASK','INDIVIDUAL_STATS_ADVISOR_TASK'); 2 no rows selected SQL> show pdbs 2 PDB advtaskswherenamein(AUTOSTATSADVISORTASK,INDIVIDUALSTATSADVISORTASK);2norowsselectedSQL>showpdbs2PDBSEED READ ONLY NO
3 PDB1 READ WRITE NO

—PDB中JOB的状态
SQL> alter session set container=pdb1;
Session altered.

SQL> select name, ctime, how_created,OWNER_NAME from sys.wri$_adv_tasks
where name in (‘AUTO_STATS_ADVISOR_TASK’,‘INDIVIDUAL_STATS_ADVISOR_TASK’);
2 AUTO_STATS_ADVISOR_TASK 26-JAN-17 CMD SYS
INDIVIDUAL_STATS_ADVISOR_TASK 26-JAN-17 CMD SYS

SQL> DECLARE
v_tname VARCHAR2(32767);
BEGIN
v_tname := ‘AUTO_STATS_ADVISOR_TASK’;
DBMS_STATS.DROP_ADVISOR_TASK(v_tname);
END;
/ 2 3 4 5 6 7
PL/SQL procedure successfully completed.

SQL> select name, ctime, how_created,OWNER_NAME from sys.wri$_adv_tasks
where name in (‘AUTO_STATS_ADVISOR_TASK’,‘INDIVIDUAL_STATS_ADVISOR_TASK’);
2 INDIVIDUAL_STATS_ADVISOR_TASK 26-JAN-17 CMD SYS

—CDB 不会影响PDB
SQL> conn / as sysdba
Connected.
SQL> EXEC DBMS_STATS.INIT_PACKAGE();
PL/SQL procedure successfully completed.

SQL> select name, ctime, how_created,OWNER_NAME from sys.wri$_adv_tasks
where name in (‘AUTO_STATS_ADVISOR_TASK’,‘INDIVIDUAL_STATS_ADVISOR_TASK’);
2 AUTO_STATS_ADVISOR_TASK 15-NOV-19 CMD SYS
INDIVIDUAL_STATS_ADVISOR_TASK 15-NOV-19 CMD SYS

SQL> alter session set container=pdb1;
Session altered.

SQL> select name, ctime, how_created,OWNER_NAME from sys.wri$_adv_tasks
where name in (‘AUTO_STATS_ADVISOR_TASK’,‘INDIVIDUAL_STATS_ADVISOR_TASK’);
2 INDIVIDUAL_STATS_ADVISOR_TASK 26-JAN-17 CMD SYS
SQL>

问题4:PGA 限制ORA-4036

在执行统计信息收集JOB等的过程中会调用优化器统计顾问任务。
如果Statistics Advisor 任务的数据过多,有可能导致在执行统计信息收集JOB过程中引发ORA-4036.
例如输出的跟踪日志中的HEAP DUMP中qosadvCreateSu Chunk占用了较大空间,qosadvCreateSu是Statistics Advisor运行时所需的heap。

    PRIVATE HEAP SUMMARY DUMP
    2582 MB total:
      1969 MB commented, 975 KB permanent
       612 MB free (0 KB in empty extents),
        2557 MB,   2 heaps:   "callheap       "            607 MB free held
    ------------------------------------------------------
    Summary of subheaps at depth 1
    1962 MB total:
      1957 MB commented, 4805 KB permanent
      1136 KB free (0 KB in empty extents),
        1940 MB,   1 heap:    "qosadvCreateSu "           ★

可以通过定期删除Statistics Advisor 任务的数据 或者增加PGA_AGGREGATE_LIMIT的大小来解决。

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