log file switch (checkpoint incomplete)的问题定位

Posted ljbguanli

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      今天測试环境下应用慢。发现数据库出了问题,直接上AWR报告。因为是虚拟机。所以不用贴cpu的个数,能够发现负载高。

    


Snap Id
Snap Time Sessions Cursors/Session
Begin Snap: 15257 30-Jun-15 09:30:57 558 5.3
End Snap: 15258 30-Jun-15 10:00:27 582 5.7
Elapsed:   29.50 (mins)    
DB Time:   717.00 (mins)    

查看等待时间,发现日志切换在等待。

Top 10 Foreground Events by Total Wait Time

Event Waits Total Wait Time (sec) Wait Avg(ms) % DB time Wait Class
log file switch (checkpoint incomplete) 350 11.3K 32229 26.2 Configuration
db file sequential read 569,141 8433.8 15 19.6 User I/O
read by other session 1,228,260 6279.9 5 14.6 User I/O
buffer busy waits 452,194 6138 14 14.3 Concurrency
DB CPU   3121.5   7.3  
enq: TX - row lock contention 300 1934.5 6448 4.5 Application
direct path read 45,561 1647.4 36 3.8 User I/O
db file scattered read 89,177 1617.5 18 3.8 User I/O
db file parallel read 29,761 1079.4 36 2.5 User I/O
log file sync 9,864 720.7 73 1.7 Commit

半小时切换了23次,redo日志我看了一下,一个为512M。
Statistic Total per Hour
log switches (derived) 23 46.78

最直接的方法是看下数据块修改的情况,再去查SQL。一眼看去就是物化视图MV_CONTRACT_INFO导致,70,211,408是修改数据库的数量。换算成数据量是70211408*8/1024/1024=535.6G。只是这个是最大的redo。事实上真实的比这个小,即使小,也非常可观。

非常明显。是有人在刷新物化视图,通知开发不要在上班时间内刷新物化视图。

Segments by DB Blocks Changes

  • % of Capture shows % of DB Block Changes for each top segment compared
  • with total DB Block Changes for all segments captured by the Snapshot
Owner Tablespace Name Object Name Subobject Name Obj. Type DB Block Changes % of Capture
LCAM_ZC_0130 WZ MV_CONTRACT_INFO   TABLE 70,211,408 99.91
LCAM_SC SPROC4GD_DATA GCP_D_S_ALL   TABLE 34,864 0.05
LCAM_PUB_CS LCAM_SYS_TBS SYS_LOB0001127099C00014$$   LOB 5,104 0.01
LCAM_PUB_15630 WZ SOA_SERVICE_LOAD_RESULT   TABLE 5,024 0.01
LCAM_PUB_CS LCAM_SYS_TBS PK_LOAD_ID   INDEX 4,752 0.01



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