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這篇文章主要講解了“oracle數據庫CPU過高問題分析”，文中的講解內容簡單清晰，易于學習與理解，下面請大家跟著小編的思路慢慢深入，一起來研究和學習“oracle數據庫CPU過高問題分析”吧！
一、執行一條sql查詢無索引的大表，使服務器一核CPU使用近100%
SQL> select * from scott.t3 where name=dbms_random.string('u', 10);top - 19:35:32 up 1 day, 12:26, 6 users, load average: 0.15, 0.04, 0.01 Tasks: 236 total, 2 running, 234 sleeping, 0 stopped, 0 zombie Cpu0 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu1 : 99.3%us, 0.7%sy, 0.0%ni, 0.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 2039644k total, 1935220k used, 104424k free, 140204k buffers Swap: 4095992k total, 46008k used, 4049984k free, 1273692k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 20394 oracle 20 0 542m 54m 50m R 99.8 2.8 0:08.82 oracle 1 root 20 0 19396 1204 936 S 0.0 0.1 0:01.28 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 0:00.44 migration/0 4 root 20 0 0 0 0 S 0.0 0.0 0:22.40 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 0:00.04 watchdog/0 7 root RT 0 0 0 0 S 0.0 0.0 0:00.48 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 0:00.50 ksoftirqd/1 10 root RT 0 0 0 0 S 0.0 0.0 0:00.06 watchdog/1 11 root 20 0 0 0 0 S 0.0 0.0 0:13.44 events/0 12 root 20 0 0 0 0 S 0.0 0.0 0:00.51 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/0 21 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kintegrityd/1 22 root 20 0 0 0 0 S 0.0 0.0 0:00.62 kblockd/0 23 root 20 0 0 0 0 S 0.0 0.0 0:00.19 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_hotplug 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_usbd 31 root 20 0 0 0 0 S 0.0 0.0 0:00.02 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 37 root 20 0 0 0 0 S 0.0 0.0 0:00.01 khungtaskd 38 root 20 0 0 0 0 S 0.0 0.0 0:05.76 kswapd0 39 root 25 5 0 0 0 S 0.0 0.0 0:00.00 ksmd
二、通過v$sqlstats視圖根據cpu時間進行排序，查出當前CPU消耗最大的前兩條sql，可以看到排名第一的就是剛才執行的測試sql，至此，即可定位到引發高CPU的語句，下一步進行語句分析；
SQL> select * from (select s.sql_id,s.SQL_TEXT,s.CPU_TIME / 1000000 cpu from v$sqlstats s order by s.CPU_TIME desc) where rownum<=2;
SQL_IDSQL_TEXT CPU
-------------------------------------------------------------------------------------------------------
gmkaj9nz7vyvwselect * from scott.t3 where name=dbms_random.string('u', 10) 60.965731
SQL_IDSQL_TEXT CPU
-------------------------------------------------------------------------------------------------------
d2dkktkqvxhp6
SELECT T.TABLE_NAME, T.TABLESPACE_NAME, T.NUM_ROWS, TC.COMMENTS, T.LOGGING, T.TA
BLE_LOCK, T.ROW_MOVEMENT, T.CLUSTER_NAME, T.PCT_FREE, T.PCT_USED, T.INI_TRANS, T.MAX_TRANS, T.INITIAL_EXTENT, T.NEXT_EXTENT, T.MIN_EXTENTS, T.MAX_EXTENTS, T.PCT
_INCREASE, T.FREELISTS, T.FREELIST_GROUPS, T.BLOCKS, T.EMPTY_BLOCKS, T.AVG_SPACE
, T.CHAIN_CNT, T.AVG_SPACE_FREELIST_BLOCKS, T.NUM_FREELIST_BLOCKS, T.SAMPLE_SIZE
, T.GLOBAL_STATS, T.USER_STATS, T.DURATION, T.SKIP_CORRUPT, T.AVG_ROW_LEN, T.OBJ
ECT_ID_TYPE, T.TABLE_TYPE_OWNER, T.TABLE_TYPE, T.COMPRESS_FOR, T.STATUS DROP_TAB
LE_STATUS, T.COMPRESSION, T.DROPPED, T.CLUSTER_OWNER, T.DEPENDENCIES, T.IOT_NAME
, T.BACKED_UP, T.DEGREE, T.INSTANCES, T.CACHE, T.LAST_ANALYZED, T.PARTITIONED, T.IOT_TYPE, T.TEMPORARY, T.SECONDARY, T.NESTED, T.BUFFER_POOL, T.MONITORING, (SEL
ECT STATUS FROM SYS.ALL_OBJECTS WHERE OWNER = T.OWNER AND OBJECT_NAME = T.TABLE_
NAME AND OBJECT_TYPE = 'TABLE' AND SUBOBJECT_NAME IS NULL) STATUS, (SELECT GENER
ATED FROM SYS.ALL_OBJECTS WHERE OWNER =
.776882三、根據第2步得到的sqlid，通過視圖dba_hist_sql_plan可以查看到此sql的執行計劃，可以看到進行了全表掃描
SQL> select id,operation,options,object_owner,object_name,object_type,optimizer,cost,bytes,cpu_cost,time from dba_hist_sql_plan where sql_id='gmkaj9nz7vyvw'; IDOPERATIONOPTIONSOBJECT_OWNEROBJECT_NAMEOBJECT_TYPEOPTIMIZERCOST BYTES CPU_COST TIME -------------------- -------------------- ---------- ---------- ------------------------------ -------------------- ---------- ---------- ------------------------------ -------------------- ---------- ---------- ---------- 0SELECT STATEMENTALL_ROWS3632 1TABLE ACCESSFULLSCOTTT3TABLE3632836060800816736244
四、如果問題已經出現一段時間，在v$sqlstats視圖中已搜索不到數據，可以前往查看視圖dba_hist_sqlstat，里面會有歷史的sql數據記錄，根據下面sql可以查看到第四條即為剛才測試的語句，然后根據sqlid仍可至dba_hist_sql_plan視圖中查看執行計劃
SQL> select t.*,(select sql_text from dba_hist_sqltext where sql_id=t.sql_id) sql_text from (select sql_id,sum(cpu_time_total),sum(cpu_time_delta) from dba_hist_sqlstat group by sql_id order by 2 desc) t where rownum<=5;
SQL_ID SUM(CPU_TIME_TOTAL) SUM(CPU_TIME_DELTA)SQL_TEXT
--------------------------------------------------------------------------------------------- ------------------- -------------------
46hjcvyssg7a2922170810 545961002BEGIN DBMS_SQLPA.execute_analysis_task(task_name=>:sts_task); END;
5hrxg25g8bdpd502210755 308952092INSERT INTO T1 VALUES (S_T1_ID.NEXTVAL,DBMS_RANDOM.STRING('u', 10),SYSDATE)
7j89gjdpf4m4u398767377 265823588
begin
for i in 1 .. 1000000 loop
insert into t1 values (s_t1_id.Nextval,dbms_ran
gmkaj9nz7vyvw324451675 261535240select * from scott.t3 where name=dbms_random.string('u', 10)
a0qbnz3z4x4ns179105773 179105773select * from scott.t1 where name=dbms_random.string('u', 10)
SQL> select id,operation,options,object_owner,object_name,object_type,optimizer,cost,bytes,cpu_cost,time from dba_hist_sql_plan where sql_id='gmkaj9nz7vyvw'；
IDOPERATIONOPTIONSOBJECT_OWNEROBJECT_NAMEOBJECT_TYPEOPTIMIZERCOST BYTES CPU_COST TIME
-------------------- -------------------- ---------- ---------- ------------------------------ -------------------- ---------- ---------- ------------------------------ -------------------- ---------- ---------- ----------
0SELECT STATEMENTALL_ROWS3632
1TABLE ACCESSFULLSCOTTT3TABLE3632836060800816736244感謝各位的閱讀，以上就是“oracle數據庫CPU過高問題分析”的內容了，經過本文的學習后，相信大家對oracle數據庫CPU過高問題分析這一問題有了更深刻的體會，具體使用情況還需要大家實踐驗證。這里是億速云，小編將為大家推送更多相關知識點的文章，歡迎關注！
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