online redo log 一直處於active 狀態可能原因分析 [zt]

tolywang發表於2006-07-07


平臺:SunOS 5.8 Generic_108528-23 sun4u sparc SUNW,Ultra-Enterprise
資料庫:8.1.5.0.0
症狀:響應緩慢,應用請求已經無法返回

檢視redo log 大小及組數,是否合理。
登陸資料庫,發現redo日誌組除current外都處於active狀態

oracle:/oracle/oracle8>sqlplus "/ as sysdba"

SQL*Plus: Release 8.1.5.0.0 - Production on Thu Jun 23 18:56:06 2005

(c) Copyright 1999 Oracle Corporation.  All rights reserved.


Connected to:
Oracle8i Enterprise Edition Release 8.1.5.0.0 - Production
With the Partitioning and Java options
PL/SQL Release 8.1.5.0.0 - Production
SQL> select * from v$log;

    GROUP#    THREAD#  SEQUENCE#      BYTES    MEMBERS ARC STATUS           FIRST_CHANGE# FIRST_TIM
---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- ---------
         1          1     520403   31457280          1 NO  ACTIVE              1.3861E+10 23-JUN-05
         2          1     520404   31457280          1 NO  ACTIVE              1.3861E+10 23-JUN-05
         3          1     520405   31457280          1 NO  ACTIVE              1.3861E+10 23-JUN-05
         4          1     520406   31457280          1 NO  CURRENT             1.3861E+10 23-JUN-05
         5          1     520398   31457280          1 NO  ACTIVE              1.3860E+10 23-JUN-05
         6          1     520399   31457280          1 NO  ACTIVE              1.3860E+10 23-JUN-05
         7          1     520400  104857600          1 NO  ACTIVE              1.3860E+10 23-JUN-05
         8          1     520401  104857600          1 NO  ACTIVE              1.3860E+10 23-JUN-05
         9          1     520402  104857600          1 NO  ACTIVE              1.3861E+10 23-JUN-05

9 rows selected.

SQL> /

    GROUP#    THREAD#  SEQUENCE#      BYTES    MEMBERS ARC STATUS           FIRST_CHANGE# FIRST_TIM
---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- ---------
         1          1     520403   31457280          1 NO  ACTIVE              1.3861E+10 23-JUN-05
         2          1     520404   31457280          1 NO  ACTIVE              1.3861E+10 23-JUN-05
         3          1     520405   31457280          1 NO  ACTIVE              1.3861E+10 23-JUN-05
         4          1     520406   31457280          1 NO  CURRENT             1.3861E+10 23-JUN-05
         5          1     520398   31457280          1 NO  ACTIVE              1.3860E+10 23-JUN-05
         6          1     520399   31457280          1 NO  ACTIVE              1.3860E+10 23-JUN-05
         7          1     520400  104857600          1 NO  ACTIVE              1.3860E+10 23-JUN-05
         8          1     520401  104857600          1 NO  ACTIVE              1.3860E+10 23-JUN-05
         9          1     520402  104857600          1 NO  ACTIVE              1.3861E+10 23-JUN-05

9 rows selected.

如果日誌都處於active狀態,那麼顯然DBWR的寫已經無法跟上log switch觸發的檢查點。
接下來讓我們檢查一下DBWR的繁忙程度:
SQL> !
oracle:/oracle/oracle8>ps -ef|grep ora_
  oracle  2273     1  0   Mar 31 ?       57:40 ora_smon_hysms02
  oracle  2266     1  0   Mar 31 ?       811:42 ora_dbw0_hysms02
  oracle  2264     1 16   Mar 31 ?       16999:57 ora_pmon_hysms02
  oracle  2268     1  0   Mar 31 ?       1649:07 ora_lgwr_hysms02
  oracle  2279     1  0   Mar 31 ?        8:09 ora_snp1_hysms02
  oracle  2281     1  0   Mar 31 ?        4:22 ora_snp2_hysms02
  oracle  2285     1  0   Mar 31 ?        9:40 ora_snp4_hysms02
  oracle  2271     1  0   Mar 31 ?       15:57 ora_ckpt_hysms02
  oracle  2283     1  0   Mar 31 ?        5:37 ora_snp3_hysms02
  oracle  2277     1  0   Mar 31 ?        5:58 ora_snp0_hysms02
  oracle  2289     1  0   Mar 31 ?        0:00 ora_d000_hysms02
  oracle  2287     1  0   Mar 31 ?        0:00 ora_s000_hysms02
  oracle  2275     1  0   Mar 31 ?        0:04 ora_reco_hysms02
  oracle 21023 21012  0 18:52:59 pts/65   0:00 grep ora_

DBWR的程式號是2266。
使用Top命令觀察一下:
oracle:/oracle/oracle8>top

last pid: 21145;  load averages:  3.38,  3.45,  3.67               18:53:38
725 processes: 711 sleeping, 1 running, 10 zombie, 3 on cpu
CPU states: 35.2% idle, 40.1% user,  9.4% kernel, 15.4% iowait,  0.0% swap
Memory: 3072M real, 286M free, 3120M swap in use, 1146M swap free

   PID USERNAME THR PRI NICE  SIZE   RES STATE    TIME    CPU COMMAND
 11855 smspf      1  59    0 1355M 1321M cpu/0   19:32 16.52% oracle
  2264 oracle     1   0    0 1358M 1316M run    283.3H 16.36% oracle
 11280 oracle     1  13    0 1356M 1321M sleep   79.8H  0.77% oracle
  6957 smspf     15  29   10   63M   14M sleep  107.7H  0.76% java
 17393 smspf      1  30    0 1356M 1322M cpu/1  833:05  0.58% oracle
 29299 smspf      5  58    0 8688K 5088K sleep   18.5H  0.38% fee_ftp_get
 21043 oracle     1  43    0 3264K 2056K cpu/9    0:01  0.31% top
 20919 smspf     17  29   10   63M   17M sleep  247:02  0.29% java
 25124 smspf      1  58    0   16M 4688K sleep    0:35  0.25% smif_status_rec
  8086 smspf      5  23    0   21M   13M sleep   41.1H  0.24% fee_file_in
 16009 root       1  35    0 4920K 3160K sleep    0:03  0.21% sshd2
 25126 smspf      1  58    0 1355M 1321M sleep    0:26  0.20% oracle
  2266 oracle     1  60    0 1357M 1317M sleep  811:42  0.18% oracle
 11628 smspf      7  59    0 3440K 2088K sleep    0:39  0.16% sgip_client_ltz
 26257 smspf     82  59    0  447M  178M sleep  533:04  0.15% java

我們注意到,2266號程式消耗的CPU不過0.18%,顯然並不繁忙,那麼瓶頸就很可能在IO上。
使用IOSTAT工具檢查IO狀況。
gqgai:/home/gqgai>iostat -xn 3
                    extended device statistics              
    r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device
......
    0.0    0.0    0.0    0.0  0.0  0.0    0.0    0.0   0   0 c0t6d0
    1.8   38.4   32.4  281.0  0.0  0.7    0.0   16.4   0  29 c0t10d0
    1.8   38.4   32.4  281.0  0.0  0.5    0.0   13.5   0  27 c0t11d0
   24.8   61.3 1432.4  880.1  0.0  0.5    0.0    5.4   0  26 c1t1d0
    0.0    0.0    0.0    0.0  0.0  0.0    0.0    9.1   0   0 hurraysms02:vold(pid238)
                    extended device statistics              
    r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device
........
    0.0    0.0    0.0    0.0  0.0  0.0    0.0    0.0   0   0 c0t6d0
    0.3    8.3    0.3   47.0  0.0  0.1    0.0    9.2   0   8 c0t10d0
    0.0    8.3    0.0   47.0  0.0  0.1    0.0    8.0   0   7 c0t11d0
   11.7   65.3  197.2  522.2  0.0  1.6    0.0   20.5   0 100 c1t1d0
    0.0    0.0    0.0    0.0  0.0  0.0    0.0    0.0   0   0 hurraysms02:vold(pid238)
                    extended device statistics              
    r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device
........
    0.0    0.0    0.0    0.0  0.0  0.0    0.0    0.0   0   0 c0t6d0
    0.3   13.7    2.7   68.2  0.0  0.2    0.0   10.9   0  12 c0t10d0
    0.0   13.7    0.0   68.2  0.0  0.1    0.0    9.6   0  11 c0t11d0
   11.3   65.3   90.7  522.7  0.0  1.5    0.0   19.5   0  99 c1t1d0
    0.0    0.0    0.0    0.0  0.0  0.0    0.0    0.0   0   0 hurraysms02:vold(pid238)
                    extended device statistics              
    r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device
........
    0.0    0.0    0.0    0.0  0.0  0.0    0.0    0.0   0   0 c0t6d0
    0.0    8.0    0.0   42.7  0.0  0.1    0.0    9.3   0   7 c0t10d0
    0.0    8.0    0.0   42.7  0.0  0.1    0.0    9.1   0   7 c0t11d0
   11.0   65.7  978.7  525.3  0.0  1.4    0.0   17.7   0  99 c1t1d0
    0.0    0.0    0.0    0.0  0.0  0.0    0.0    0.0   0   0 hurraysms02:vold(pid238)
                    extended device statistics              
    r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device
........
    0.0    0.0    0.0    0.0  0.0  0.0    0.0    0.0   0   0 c0t6d0
    0.3   87.7    2.7  433.7  0.0  2.2    0.0   24.9   0  90 c0t10d0
    0.0   88.3    0.0  436.5  0.0  1.8    0.0   19.9   0  81 c0t11d0
   89.0   54.0  725.4  432.0  0.0  2.1    0.0   14.8   0 100 c1t1d0
    0.0    0.0    0.0    0.0  0.0  0.0    0.0    0.0   0   0 hurraysms02:vold(pid238)


我們注意到,存放資料庫的主要卷c1t1d0的繁忙程度始終處於99~100,而寫速度卻只有500K/s左右,這個速度是極為緩慢的。
(%b percent of time the disk is busy (transactions in progress)
Kw/s kilobytes written per second)
根據我們的常識T3盤陣通常按Char寫速度可以達到10M/s左右,以前測試過一些Tpcc指標,可以參考:

而正常情況下的資料庫隨機寫通常都在1~2M左右,顯然此時的磁碟已經處於不正常狀態,經過確認的確是硬碟發生了損壞,Raid5的Group中損壞了一塊硬碟。
經過更換以後系統逐漸恢復正常。

來自 “ ITPUB部落格 ” ,連結:http://blog.itpub.net/35489/viewspace-84411/,如需轉載,請註明出處,否則將追究法律責任。

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