oracle数据库CPU过高问题定位、分析（一）
top - 00:05:18 up 21:37, 7 users, load average: 0.54, 0.17, 0.14 Tasks: 236 total, 3 running, 233 sleeping, 0 stopped, 0 zombie Cpu0 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0 Cpu1 : 99.7%us, 0.3%sy, 0.0%ni, 0.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0 Mem: 2039644k total, 1935444k used, 104200k free, 10604k buffers Swap: 4095992k total, 41048k used, 4054944k free, 1473288k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 14468 oracle 20 0 540m 46m 43m R 100.0 2.4 0:17.76 oracle 14470 oracle 20 0 540m 26m 23m R 99.8 1.4 0:16.51 oracle 1 root 20 0 19396 1184 916 S 0.0 0.1 0:00.88 init 2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd 3 root RT 0 0 0 0 S 0.0 0.0 0:00.31 migration/0 4 root 20 0 0 0 0 S 0.0 0.0 0:22.38 ksoftirqd/0 5 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/0 6 root RT 0 0 0 0 S 0.0 0.0 0:00.02 watchdog/0 7 root RT 0 0 0 0 S 0.0 0.0 0:00.32 migration/1 8 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/1 9 root 20 0 0 0 0 S 0.0 0.0 0:00.31 ksoftirqd/1 10 root RT 0 0 0 0 S 0.0 0.0 0:00.03 watchdog/1 11 root 20 0 0 0 0 S 0.0 0.0 0:13.22 events/0 12 root 20 0 0 0 0 S 0.0 0.0 0:00.23 events/1 13 root 20 0 0 0 0 S 0.0 0.0 0:00.00 cpuset 14 root 20 0 0 0 0 S 0.0 0.0 0:00.00 khelper 15 root 20 0 0 0 0 S 0.0 0.0 0:00.00 netns 16 root 20 0 0 0 0 S 0.0 0.0 0:00.00 async/mgr 17 root 20 0 0 0 0 S 0.0 0.0 0:00.00 pm 18 root 20 0 0 0 0 S 0.0 0.0 0:00.00 sync_supers 19 root 20 0 0 0 0 S 0.0 0.0 0:00.00 bdi-default 20 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kintegrityd/ 21 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kintegrityd/ 22 root 20 0 0 0 0 S 0.0 0.0 0:00.53 kblockd/0 23 root 20 0 0 0 0 S 0.0 0.0 0:00.11 kblockd/1 24 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kacpid 25 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kacpi_notify 26 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kacpi_hotplu 27 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ata/0 28 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ata/1 29 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ata_aux 30 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ksuspend_usb 31 root 20 0 0 0 0 S 0.0 0.0 0:00.01 khubd 32 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kseriod 33 root 20 0 0 0 0 S 0.0 0.0 0:00.00 md/0 34 root 20 0 0 0 0 S 0.0 0.0 0:00.00 md/1 35 root 20 0 0 0 0 S 0.0 0.0 0:00.00 md_misc/0 36 root 20 0 0 0 0 S 0.0 0.0 0:00.00 md_misc/1
通过top监控可以发现服务器的CPU被oracle进程14468与14470给消耗殆尽
一、定位问题
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1、通过PID与v$process、v$session两张视图快速定位出语句的sql_id，如下：
SQL> select sql_id from v$session where paddr= (select addr from v$process where spid ='14468');
SQL_ID
-------------
gmkaj9nz7vyvw
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2、通过sql_id查看具体sql
SQL> select sql_text from v$sql where sql_id='gmkaj9nz7vyvw';
SQL_TEXT
--------------------------------------------------------------------------------
select * from scott.t3 where name=dbms_random.string('u', 10)
二、分析问题
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A、通过oracle工具脚本awrsqrpt.sql分析具体sql
SQL> @awrsqrpt Current Instance ~~~~~~~~~~~~~~~~ DB Id DB Name Inst Num Instance ----------- ------------ -------- ------------ 1506959389 ORCL1 orcl Specify the Report Type ~~~~~~~~~~~~~~~~~~~~~~~ Would you like an HTML report, or a plain text report? Enter 'html' for an HTML report, or 'text' for plain text Defaults to 'html' Enter value for report_type: Type Specified: html Instances in this Workload Repository schema ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DB Id Inst Num DB Name InstanceHost ------------ -------- ------------ ------------ ------------ * 1506959389 1 ORCL orcl localhost.lo caldomain Using 1506959389 for database Id Using 1 for instance number Specify the number of days of snapshots to choose from ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Entering the number of days (n) will result in the most recent (n) days of snapshots being listed. Pressingwithout specifying a number lists all completed snapshots. Enter value for num_days: Listing all Completed Snapshots Snap Instance DB Name Snap Id Snap Started Level ------------ ------------ --------- ------------------ ----- orcl ORCL 21 25 Jul 2018 22:30 1 22 25 Jul 2018 23:42 1 23 25 Jul 2018 23:45 1 24 25 Jul 2018 23:47 1 25 25 Jul 2018 23:49 1 26 25 Jul 2018 23:51 1 27 26 Jul 2018 00:04 1 28 26 Jul 2018 00:07 1 29 26 Jul 2018 00:08 1 30 26 Jul 2018 00:09 1 31 26 Jul 2018 18:49 1 32 26 Jul 2018 19:11 1 33 26 Jul 2018 19:16 1 Specify the Begin and End Snapshot Ids ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Enter value for begin_snap: 32 Begin Snapshot Id specified: 32 Enter value for end_snap: 33 End Snapshot Id specified: 33 Specify the SQL Id ~~~~~~~~~~~~~~~~~~ Enter value for sql_id: gmkaj9nz7vyvw SQL ID specified: gmkaj9nz7vyvw Specify the Report Name ~~~~~~~~~~~~~~~~~~~~~~~ The default report file name is awrsqlrpt_1_32_33.html. To use this name, press to continue, otherwise enter an alternative. Enter value for report_name: /home/oracle/awrsql1.html Using the report name /home/oracle/awrsql1.html
查看生成的html结果
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B、通过dbms_xplan.display_awr与sql_id查看语句详情
SQL> select * from table(dbms_xplan.display_awr('gmkaj9nz7vyvw'));
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
SQL_ID gmkaj9nz7vyvw
--------------------
select * from scott.t3 where name=dbms_random.string('u', 10)
Plan hash value: 4161002650
--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 3632 (100)| |
| 1 | TABLE ACCESS FULL| T3 | 24590 | 816K| 3632 (6)| 00:00:44 |
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
--------------------------------------------------------------------------
Note
-----
- dynamic sampling used for this statement (level=2)
17 rows selected.
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C、通过sql语句直接分析
SQL> explain plan for select * from scott.t3 where name=dbms_random.string('u', 10);
Explained.
SQL> select * from table(dbms_xplan.display());
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Plan hash value: 4161002650
--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 24590 | 816K| 3632 (6)| 00:00:44 |
|* 1 | TABLE ACCESS FULL| T3 | 24590 | 816K| 3632 (6)| 00:00:44 |
--------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
1 - filter("NAME"="DBMS_RANDOM"."STRING"('u',10))
Note
-----
- dynamic sampling used for this statement (level=2)
17 rows selected.
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