Oracle数据库诊断案例-redo log日志组处于高激活状态

作者:eygle
出处: http://www.eygle.com/blog
日期:June 26, 2005
本文链接: http://www.eygle.com/archives/2005/06/oracleeaoieiear.html

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平台:SunOS 5.8 Generic_108528-23 sun4u sparc SUNW,Ultra-Enterprise
数据库:8.1.5.0.0
症状:响应缓慢，应用请求已经无法返回
登陆数据库,发现redo日志组除current外都处于active状态

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.

如果日志都处于active状态，那么显然DBWR的写已经无法跟上log switch触发的检查点。

接下来让我们检查一下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的进程号是2266。
使用Top命令观察一下:

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

我们注意到，2266号进程消耗的CPU不过0.18%,显然并不繁忙,那么瓶颈就很可能在IO上。
使用IOSTAT工具检查IO状况。

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)

我们注意到，存放数据库的主要卷c1t1d0的繁忙程度始终处于99~100,而写速度却只有500K/s左右，这个速度是极为缓慢的。
(%b percent of time the disk is busy (transactions in progress)
Kw/s kilobytes written per second)
根据我们的常识T3盘阵通常按Char写速度可以达到10M/s左右，以前测试过一些Tpcc指标，可以参考: Use bonnie to Test system IO speed。
而正常情况下的数据库随机写通常都在1~2M左右，显然此时的磁盘已经处于不正常状态，经过确认的确是硬盘发生了损坏，Raid5的Group中损坏了一块硬盘。
经过更换以后系统逐渐恢复正常。

Posted by eygle at June 26, 2005