oracle数据库CPU过高问题定位、分析（总结）
一、为ASH、AWR、ADDM、SPA分别开启会话，并使用会话跟踪：
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--ASH
alter session set events '10046 trace name context forever,level 12'; Session altered. SQL> @ashrpt SQL> alter session set events '10046 trace name context off';
--AWR
SQL> alter session set events '10046 trace name context forever,level 12'; Session altered. SQL> @awrrpt SQL> alter session set events '10046 trace name context off';
--ADDM
SQL> alter session set events '10046 trace name context forever,level 12';
Session altered.
SQL> var task_name varchar2(30);
SQL> exec DBMS_ADDM.ANALYZE_DB(:task_name,57,58);
PL/SQL procedure successfully completed.
SQL> print :task_name
TASK_NAME
--------------------------------------------------------------------------------
TASK_366
SQL> set long 1000000 pagesize 0;
SQL> select dbms_addm.get_report('TASK_366') from dual;
SQL> alter session set events '10046 trace name context off';
--SPA
SQL> alter session set events '10046 trace name context forever,level 12';
SQL> begin
dbms_sqltune.create_sqlset(
sqlset_name=>'cpu_2',
description => 'High cpu read tuning set');
end;
/ 2 3 4 5 6
PL/SQL procedure successfully completed.
SQL> declare
base_cur dbms_sqltune.sqlset_cursor;
begin
open base_cur for
select value(x) from table(DBMS_SQLTUNE.select_workload_repository(57,58,NULL,NULL,'cpu_time',NULL,NULL,NULL,10)) x;
--
dbms_sqltune.load_sqlset(sqlset_name=>'cpu_2',populate_ 2 3 4 5 6 7 cursor => base_cur);
end;
/ 8 9
PL/SQL procedure successfully completed.
SQL> variable sts_task VARCHAR2(64);
SQL> EXEC :sts_task :=DBMS_SQLPA.CREATE_ANALYSIS_TASK(sqlset_name=>'cpu_2',order_by=>'cpu_time',description=>'process workload ordered by cpu_time');
PL/SQL procedure successfully completed.
SQL> EXEC DBMS_SQLPA.execute_analysis_task(task_name=>:sts_task,execution_type=>'CONVERT SQLSET',execution_params=>dbms_advisor.arglist('TIME_LIMIT','1800'));
PL/SQL procedure successfully completed.
SQL> set long 1000000 pagesize 0;
SQL> select DBMS_SQLPA.report_analysis_task(:sts_task,'HTML','ALL','ALL') from dual;
SQL> alter session set events '10046 trace name context off';
二、通过tkprof解析跟踪文件
tkprof orcl_ora_21955.trc /home/oracle/ash.txt
tkprof orcl_ora_22077.trc /home/oracle/awr.txt
tkprof orcl_ora_22087.trc /home/oracle/addm.txt
tkprof orcl_ora_22092.trc /home/oracle/spa.txt
三、查看解析结果
--ASH
call count cpu elapsed disk query current rows ------- ------ -------- ---------- ---------- ---------- ---------- ---------- Parse 1041 0.39 0.39 0 252 0 0 Execute 1165 2.42 2.43 0 3352 7 12 Fetch 2426 0.09 0.07 81 4688 126 1848 ------- ------ -------- ---------- ---------- ---------- ---------- ---------- total 4632 2.90 2.90 81 8292 133 1860
--AWR
call count cpu elapsed disk query current rows ------- ------ -------- ---------- ---------- ---------- ---------- ---------- Parse 1386 0.19 0.19 0 14 0 0 Execute 3630 0.81 0.81 1 1213 8 1 Fetch 9177 0.30 0.41 195 118457 3421 7597 ------- ------ -------- ---------- ---------- ---------- ---------- ---------- total 14193 1.31 1.42 196 119684 3429 7598
--ADDM
call count cpu elapsed disk query current rows ------- ------ -------- ---------- ---------- ---------- ---------- ---------- Parse 555 0.03 0.03 0 74 0 0 Execute 1915 0.16 0.16 5 2294 322 91 Fetch 4988 0.04 0.03 0 10032 3 4861 ------- ------ -------- ---------- ---------- ---------- ---------- ---------- total 7458 0.24 0.23 5 12400 325 4952
--SPA
call count cpu elapsed disk query current rows ------- ------ -------- ---------- ---------- ---------- ---------- ---------- Parse 1311 0.11 0.12 0 507 0 0 Execute 4131 0.41 0.51 15 7701 850 232 Fetch 10741 0.13 0.16 16 32068 4 10646 ------- ------ -------- ---------- ---------- ---------- ---------- ---------- total 16183 0.66 0.80 31 40276 854 10878
四、分析结果
通过上述结果可以发现，
query(buffer)的使用消耗优先排列为：ash=>addm=>spa=>awr
disk（磁盘）的使用消耗优先排列为：addm=>ash=>spa=>addm
cpu的使用消耗优先排列为：addm=>spa=>awr=>ash
生产环境定位问题时，可以将上述结果作为参考，避免CPU过高时仍使用cpu消耗过大的工具；【实验中ash的取时范围为1小时，生产环境中往往使用ash皆是查看几分钟的区间，因此ash的性能消耗是最低的】
五、关于性能视图与会话跟踪，性能消耗相对更低，但可阅读性相比上述工具略差，可根据个人习惯进行选择
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