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做微博网站,seo关键词词库,合肥网站推广哪家好,电影html网页模板设计素材ORACLE DML执行计划频繁变更导致业务响应极慢问题的处理发布时间：2020-08-08 17:51:00来源：ITPUB博客阅读：167作者：清风艾艾最近，oracle rac维护中遇到一件很奇怪的事情，就是业务偶尔会出现极其缓慢的情况&…

ORACLE DML执行计划频繁变更导致业务响应极慢问题的处理

发布时间：2020-08-08 17:51:00

来源：ITPUB博客

阅读：167

作者：清风艾艾

最近，oracle rac维护中遇到一件很奇怪的事情，就是业务偶尔会出现极其缓慢的情况，查看服务器负载、数据库负载却很低，数据库和主机日志也没有明显报错，数据库内部也没有拥堵会话的情况。本文特此记录，以备后查！

背景：从12月份开始，应用开始反馈，没次做新品发布，下发单据就会特别慢，后来为了临时解决问题，将业务指向到单节点，发现业务下发速度恢复正常。后来，过了一周左右的时间，单据下发速度再次很慢。但是，

查看服务器负载、数据库负载却很低，数据库和主机日志也没有明显报错，数据库内部也没有拥堵会话的情况。为了尽快恢复业务，重启了数据库服务，

业务暂时恢复正常。然而，三四天之后，也就是今天，又出现下发单据缓慢的情况。

问题分析：

1、基于以上背景，数据库和主机没有高负载，尤其是数据库内部没有会话拥堵的情况，我能想到的是SQL执行计划可能出现了变化。

2、查看业务承载节点，在执行的SQL语句

3、查看sql-5216pwt38ckhp的执行计划

--优秀的执行计划，一次单据下发3-8点能执行近30次

--变化后的低效执行计划，一次单据下发3-10点，执行只有1完多次

4、通过步骤3中变化前后的执行计划对比，我们发现

--变化前的执行计划走的主键唯一索引扫描，变化后的执行计划走的普通索引的范围扫描

--变化前的执行计划buffer get很低为11，且没有磁盘读，变化后的执行计划buffer很高为28万，出现了磁盘物理读

--变化前的执行计划唯一索引扫描后回表扫描一行数据，变化后的执行计划对索引全分区扫描后回表扫描一行数据

--变化前的执行计划单次单据下发3-8点能执行近30完成，变化后的执行计划单次单据下发3-10点才执行1万多次

问题处理：

基于以上问题分析，SQL-5216pwt38ckhp语句是update语句，且使用了绑定变量，因此，在不改变sql的情况下，我们

选择固定sql的执行计划。方法是使用脚本coe_load_sql_profile.sql进行执行计划固定，在执行计划固定的时候需要注意，

不能以sys登陆数据库执行固话执行计划，需要使用业务用户执行，固话过程中，需要输入两次sql_id，然后选择优异执行计划的plan hash value即可。

附上执行计划固定脚本coe_load_sql_profile.sql：

SPO coe_load_sql_profile.log;

SET DEF ON TERM OFF ECHO ON FEED OFF VER OFF HEA ON LIN 2000 PAGES 100 LONG 8000000 LONGC 800000 TRIMS ON TI OFF TIMI OFF SERVEROUT ON SIZE 1000000 NUM 20 SQLP SQL>;

SET SERVEROUT ON SIZE UNL;

REM

REM $Header: 215187.1 coe_load_sql_profile.sql 11.4.5.5 2013/03/01 carlos.sierra $

REM

REM AUTHOR

REM carlos.sierra@oracle.com

REM

REM SCRIPT

REM coe_load_sql_profile.sql

REM

REM DESCRIPTION

REM This script loads a plan from a modified SQL into a Custom SQL

REM Profile for the original SQL.

REM If a good performing plan only reproduces with CBO Hints

REM then you can load the plan of the modified version of the

REM SQL into a Custom SQL Profile for the orignal SQL.

REM In other words, the original SQL can use the plan that was

REM generated out of the SQL with hints.

REM

REM PRE-REQUISITES

REM 1. Have in cache or AWR the text for the original SQL.

REM 2. Have in cache or AWR the plan for the modified SQL

REM (usually with hints).

REM

REM PARAMETERS

REM 1. ORIGINAL_SQL_ID (required)

REM 2. MODIFIED_SQL_ID (required)

REM 3. PLAN_HASH_VALUE (required)

REM

REM EXECUTION

REM 1. Connect into SQL*Plus as user with access to data dictionary

REM and privileges to create SQL Profiles. Do not use SYS.

REM 2. Execute script coe_load_sql_profile.sql passing first two

REM parameters inline or until requested by script.

REM 3. Provide plan hash value of the modified SQL when asked.

REM 4. Use a DBA user but not SYS. Do not connect as SYS as the staging

REM table cannot be created in SYS schema and you will receive an error:

REM ORA-19381: cannot create staging table in SYS schema

REM

REM EXAMPLE

REM # sqlplus system

REM SQL> START coe_load_sql_profile.sql gnjy0mn4y9pbm b8f3mbkd8bkgh

REM SQL> START coe_load_sql_profile.sql;

REM

REM NOTES

REM 1. This script works on 10g or higher.

REM 2. For a similar script for 11g use coe_load_sql_baseline.sql,

REM which uses SQL Plan Baselines instead of Custom SQL Profiles.

REM 3. For possible errors see coe_load_sql_profile.log

REM 4. If you get "ORA-06532: Subscript outside of limit, ORA-06512: at line 1"

REM Then you may consider this change (only in a test and disposable system):

REM create or replace TYPE sys.sqlprof_attr AS VARRAY(5000) of VARCHAR2(500);

REM

SET TERM ON ECHO OFF;

PRO

PRO Parameter 1:

PRO ORIGINAL_SQL_ID (required)

PRO

DEF original_sql_id = '&1';

PRO

PRO Parameter 2:

PRO MODIFIED_SQL_ID (required)

PRO

DEF modified_sql_id = '&2';

PRO

WITH

p AS (

SELECT plan_hash_value

FROM gv$sql_plan

WHERE sql_id = TRIM('&&modified_sql_id.')

AND other_xml IS NOT NULL

UNION

SELECT plan_hash_value

FROM dba_hist_sql_plan

WHERE sql_id = TRIM('&&modified_sql_id.')

AND other_xml IS NOT NULL ),

m AS (

SELECT plan_hash_value,

SUM(elapsed_time)/SUM(executions) avg_et_secs

FROM gv$sql

WHERE sql_id = TRIM('&&modified_sql_id.')

AND executions > 0

GROUP BY

plan_hash_value ),

a AS (

SELECT plan_hash_value,

SUM(elapsed_time_total)/SUM(executions_total) avg_et_secs

FROM dba_hist_sqlstat

WHERE sql_id = TRIM('&&modified_sql_id.')

AND executions_total > 0

GROUP BY

plan_hash_value )

SELECT p.plan_hash_value,

ROUND(NVL(m.avg_et_secs, a.avg_et_secs)/1e6, 3) avg_et_secs

FROM p, m, a

WHERE p.plan_hash_value = m.plan_hash_value(+)

AND p.plan_hash_value = a.plan_hash_value(+)

ORDER BY

avg_et_secs NULLS LAST;

PRO

PRO Parameter 3:

PRO PLAN_HASH_VALUE (required)

PRO

DEF plan_hash_value = '&3';

PRO

PRO Values passed to coe_load_sql_profile:

PRO ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

PRO ORIGINAL_SQL_ID: "&&original_sql_id."

PRO MODIFIED_SQL_ID: "&&modified_sql_id."

PRO PLAN_HASH_VALUE: "&&plan_hash_value."

PRO

WHENEVER SQLERROR EXIT SQL.SQLCODE;

SET TERM OFF ECHO ON;

-- trim parameters

COL original_sql_id NEW_V original_sql_id FOR A30;

COL modified_sql_id NEW_V modified_sql_id FOR A30;

COL plan_hash_value NEW_V plan_hash_value FOR A30;

SELECT TRIM('&&original_sql_id.') original_sql_id, TRIM('&&modified_sql_id.') modified_sql_id, TRIM('&&plan_hash_value.') plan_hash_value FROM DUAL;

-- open log file

SPO coe_load_sql_profile_&&original_sql_id..log;

GET coe_load_sql_profile.log;

-- get user

COL connected_user NEW_V connected_user FOR A30;

SELECT USER connected_user FROM DUAL;

VAR sql_text CLOB;

VAR other_xml CLOB;

VAR signature NUMBER;

VAR name VARCHAR2(30);

EXEC :sql_text := NULL;

EXEC :other_xml := NULL;

EXEC :signature := NULL;

EXEC :name := NULL;

-- get sql_text from memory

DECLARE

l_sql_text VARCHAR2(32767);

BEGIN -- 10g see bug 5017909

FOR i IN (SELECT DISTINCT piece, sql_text

FROM gv$sqltext_with_newlines

WHERE sql_id = TRIM('&&original_sql_id.')

ORDER BY 1, 2)

LOOP

IF :sql_text IS NULL THEN

DBMS_LOB.CREATETEMPORARY(:sql_text, TRUE);

DBMS_LOB.OPEN(:sql_text, DBMS_LOB.LOB_READWRITE);

END IF;

l_sql_text := REPLACE(i.sql_text, CHR(00), ' ');

DBMS_LOB.WRITEAPPEND(:sql_text, LENGTH(l_sql_text), l_sql_text);

END LOOP;

IF :sql_text IS NOT NULL THEN

DBMS_LOB.CLOSE(:sql_text);

END IF;

EXCEPTION

WHEN OTHERS THEN

DBMS_OUTPUT.PUT_LINE('getting original sql_text from memory: '||SQLERRM);

:sql_text := NULL;

END;

-- get sql_text from awr

BEGIN

IF :sql_text IS NULL OR NVL(DBMS_LOB.GETLENGTH(:sql_text), 0) = 0 THEN

SELECT REPLACE(sql_text, CHR(00), ' ')

INTO :sql_text

FROM dba_hist_sqltext

WHERE sql_id = TRIM('&&original_sql_id.')

AND sql_text IS NOT NULL

AND ROWNUM = 1;

END IF;

EXCEPTION

WHEN OTHERS THEN

DBMS_OUTPUT.PUT_LINE('getting original sql_text from awr: '||SQLERRM);

:sql_text := NULL;

END;

-- sql_text as found

SELECT :sql_text FROM DUAL;

-- check is sql_text for original sql is available

SET TERM ON;

BEGIN

IF :sql_text IS NULL THEN

RAISE_APPLICATION_ERROR(-20100, 'SQL_TEXT for original SQL_ID &&original_sql_id. was not found in memory (gv$sqltext_with_newlines) or AWR (dba_hist_sqltext).');

END IF;

END;

SET TERM OFF;

-- get other_xml from memory

BEGIN

FOR i IN (SELECT other_xml

FROM gv$sql_plan

WHERE sql_id = TRIM('&&modified_sql_id.')

AND plan_hash_value = TO_NUMBER(TRIM('&&plan_hash_value.'))

AND other_xml IS NOT NULL

ORDER BY

child_number, id)

LOOP

:other_xml := i.other_xml;

EXIT; -- 1st

END LOOP;

EXCEPTION

WHEN OTHERS THEN

DBMS_OUTPUT.PUT_LINE('getting modified other_xml from memory: '||SQLERRM);

:other_xml := NULL;

END;

-- get other_xml from awr

BEGIN

IF :other_xml IS NULL OR NVL(DBMS_LOB.GETLENGTH(:other_xml), 0) = 0 THEN

FOR i IN (SELECT other_xml

FROM dba_hist_sql_plan

WHERE sql_id = TRIM('&&modified_sql_id.')

AND plan_hash_value = TO_NUMBER(TRIM('&&plan_hash_value.'))

AND other_xml IS NOT NULL

ORDER BY

id)

LOOP

:other_xml := i.other_xml;

EXIT; -- 1st

END LOOP;

END IF;

EXCEPTION

WHEN OTHERS THEN

DBMS_OUTPUT.PUT_LINE('getting modified other_xml from awr: '||SQLERRM);

:other_xml := NULL;

END;

-- other_xml as found

SELECT :other_xml FROM DUAL;

-- validate other_xml

SET TERM ON;

BEGIN

IF :other_xml IS NULL THEN

RAISE_APPLICATION_ERROR(-20101, 'PLAN for modified SQL_ID &&modified_sql_id. and PHV &&plan_hash_value. was not found in memory (gv$sql_plan) or AWR (dba_hist_sql_plan).');

END IF;

END;

SET ECHO OFF;

DECLARE

h SYS.SQLPROF_ATTR := SYS.SQLPROF_ATTR ();

idx INTEGER := 0;

l_pos NUMBER;

l_hint VARCHAR2(32767);

description VARCHAR2(500);

PROCEDURE add_hint (p_hint IN VARCHAR2)

BEGIN

idx := idx + 1;

DBMS_OUTPUT.PUT_LINE(LPAD(idx, 4, '0')||' '||p_hint);

h.EXTEND;

h(idx) := p_hint;

END add_hint;

BEGIN

add_hint('BEGIN_OUTLINE_DATA');

FOR i IN (SELECT /*+ opt_param('parallel_execution_enabled', 'false') */

SUBSTR(EXTRACTVALUE(VALUE(d), '/hint'), 1, 4000) hint

FROM TABLE(XMLSEQUENCE(EXTRACT(XMLTYPE(:other_xml), '/*/outline_data/hint'))) d)

LOOP

l_hint := i.hint;

WHILE NVL(LENGTH(l_hint), 0) > 0

LOOP

IF LENGTH(l_hint) <= 500 THEN

add_hint(l_hint);

l_hint := NULL;

ELSE

l_pos := INSTR(SUBSTR(l_hint, 1, 500), ' ', -1);

add_hint(SUBSTR(l_hint, 1, l_pos));

l_hint := ' '||SUBSTR(l_hint, l_pos);

END IF;

END LOOP;

add_hint('END_OUTLINE_DATA');

:signature := DBMS_SQLTUNE.SQLTEXT_TO_SIGNATURE(:sql_text);

:name := UPPER(TRIM('&&original_sql_id.'))||'_'||TRIM('&&plan_hash_value.');

description := UPPER('original:'||TRIM('&&original_sql_id.')||' modified:'||TRIM('&&modified_sql_id.')||' phv:'||TRIM('&&plan_hash_value.')||' signature:'||:signature||' created by coe_load_sql_profile.sql');

-- create custom sql profile for original sql using plan from modified sql

DBMS_SQLTUNE.IMPORT_SQL_PROFILE (

sql_text => :sql_text, -- original sql

profile => h, -- plan from modified sql

name => :name,

description => description,

category => 'DEFAULT',

validate => TRUE,

replace => TRUE,

force_match => FALSE /* TRUE:FORCE (match even when different literals in SQL). FALSE:EXACT (similar to CURSOR_SHARING) */ );

-- drop sql profile staging table for original sql (if one exists)

BEGIN

DBMS_OUTPUT.PUT_LINE('dropping staging table "STGTAB_SQLPROF_'||UPPER(TRIM('&&original_sql_id.'))||'"');

EXECUTE IMMEDIATE 'DROP TABLE STGTAB_SQLPROF_'||UPPER(TRIM('&&original_sql_id.'));

EXCEPTION

WHEN OTHERS THEN

DBMS_OUTPUT.PUT_LINE('staging table "STGTAB_SQLPROF_'||UPPER(TRIM('&&original_sql_id.'))||'" did not exist');

END;

-- create sql profile staging table for original sql

DBMS_OUTPUT.PUT_LINE('creating staging table "STGTAB_SQLPROF_'||UPPER(TRIM('&&original_sql_id.'))||'"');

DBMS_SQLTUNE.CREATE_STGTAB_SQLPROF (

table_name => 'STGTAB_SQLPROF_'||UPPER(TRIM('&&original_sql_id.')),

schema_name => '&&connected_user.' );

-- packs new sql profile for original sql

DBMS_OUTPUT.PUT_LINE('packaging new sql profile into staging table "STGTAB_SQLPROF_'||UPPER(TRIM('&&original_sql_id.'))||'"');

DBMS_SQLTUNE.PACK_STGTAB_SQLPROF (

profile_name => :name,

staging_table_name => 'STGTAB_SQLPROF_'||UPPER(TRIM('&&original_sql_id.')),

staging_schema_owner => '&&connected_user.' );

END;

-- profile_name

COL profile_name NEW_V profile_name FOR A30;

SELECT :name profile_name FROM DUAL;

-- display details of new sql_profile

SET ECHO ON;

REM

REM SQL Profile

REM ~~~~~~~~~~~

REM

SELECT signature, name, category, type, status

FROM dba_sql_profiles WHERE name = :name;

SELECT description

FROM dba_sql_profiles WHERE name = :name;

SET ECHO OFF;

PRO

PRO ****************************************************************************

PRO * Enter &&connected_user. password to export staging table STGTAB_SQLPROF_&&original_sql_id.

PRO ****************************************************************************

HOS exp &&connected_user. tables=&&connected_user..STGTAB_SQLPROF_&&original_sql_id. file=STGTAB_SQLPROF_&&original_sql_id..dmp statistics=NONE indexes=N constraints=N grants=N triggers=N

PRO

PRO If you need to implement this Custom SQL Profile on a similar system,

PRO import and unpack using these commands:

PRO

PRO imp &&connected_user. file=STGTAB_SQLPROF_&&original_sql_id..dmp tables=STGTAB_SQLPROF_&&original_sql_id. ignore=Y

PRO

PRO BEGIN

PRO DBMS_SQLTUNE.UNPACK_STGTAB_SQLPROF (

PRO profile_name => '&&profile_name.',

PRO replace => TRUE,

PRO staging_table_name => 'STGTAB_SQLPROF_&&original_sql_id.',

PRO staging_schema_owner => '&&connected_user.' );;

PRO END;;

PRO /

PRO

SPO OFF;

HOS zip -m coe_load_sql_profile_&&original_sql_id. coe_load_sql_profile_&&original_sql_id..log STGTAB_SQLPROF_&&original_sql_id..dmp coe_load_sql_profile.log

HOS zip -d coe_load_sql_profile_&&original_sql_id. coe_load_sql_profile.log

WHENEVER SQLERROR CONTINUE;

SET DEF ON TERM ON ECHO OFF FEED 6 VER ON HEA ON LIN 80 PAGES 14 LONG 80 LONGC 80 TRIMS OFF TI OFF TIMI OFF SERVEROUT OFF NUM 10 SQLP SQL>;

SET SERVEROUT OFF;

UNDEFINE 1 2 3 original_sql_id modified_sql_id plan_hash_value profile_name

CL COL

PRO

PRO coe_load_sql_profile completed.

问题处理结果：