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最近在看一些Oracle分享的时候,经常提到导出ASH的dump给另外的人来做分析,但我没有什么相关的操作,不知道是怎样的一个操作流程,于是上网看了各种博文。于是自己动手做实验做一次导出导入。
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实验环境:Oracle 11.2.0.4+rhel 7.2
执行下面的语句对ASH信息做dump操作
sys@ORA11G>alter system set events 'immediate trace name ashdump level 10';
上面的语句中level的意思是dump出ASH buffer中最近n分钟的数据,这里以10分钟为例。
使用下面的语句打到对应的trace文件
sys@ORA11G>SELECT value FROM v$diag_info WHERE name = 'Default Trace File'; VALUE ------------------------------------------------------------------- /u01/app/oracle/diag/rdbms/ora11g/ora11g/trace/ora11g_ora_7556.trc
先简单查看一下trace文件中的内容:
从上面的两个图中可以看到trace文件中包含了三类信息:trace的基本信息、导入dump的方法和ash的实际数据,其实只要按照trace中的文件给出的方法就可以很容易的把dump数据导入到数据库中。
1、创建临时表
CREATE TABLE ashdump AS SELECT * FROM SYS.WRH$_ACTIVE_SESSION_HISTORY WHERE rownum < 0;
2、生成sqlldr的control file
[oracle@rhel7 ash]$ sed -n '1,/^Step 2:/d;/^Step 3:/,$d;p' ora11g_ora_7556.trc |sed '/^-/d' > ashldr.ctl
3、使用sqlldr工具把trace文件中的数据导入到临时表中
[oracle@rhel7 ash]$ sqlldr zx/zx control=ashldr.ctl data=ora11g_ora_7556.trc errors=1000000 SQL*Loader: Release 11.2.0.4.0 - Production on Sat Sep 23 17:16:40 2017 Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved. Commit point reached - logical record count 19 Commit point reached - logical record count 37 Commit point reached - logical record count 55 Commit point reached - logical record count 73 Commit point reached - logical record count 91 Commit point reached - logical record count 109 Commit point reached - logical record count 127 Commit point reached - logical record count 145 Commit point reached - logical record count 163 Commit point reached - logical record count 181 Commit point reached - logical record count 199 Commit point reached - logical record count 217 Commit point reached - logical record count 235 Commit point reached - logical record count 253 Commit point reached - logical record count 271 Commit point reached - logical record count 289 Commit point reached - logical record count 307 Commit point reached - logical record count 325 Commit point reached - logical record count 343 Commit point reached - logical record count 361 Commit point reached - logical record count 379 Commit point reached - logical record count 397 Commit point reached - logical record count 415 Commit point reached - logical record count 433 Commit point reached - logical record count 451 Commit point reached - logical record count 469 Commit point reached - logical record count 487 Commit point reached - logical record count 505 Commit point reached - logical record count 523 Commit point reached - logical record count 541 Commit point reached - logical record count 559 Commit point reached - logical record count 577 Commit point reached - logical record count 595 Commit point reached - logical record count 613 Commit point reached - logical record count 631 Commit point reached - logical record count 649 Commit point reached - logical record count 651 zx@ORA11G>select count(*) from ashdump; COUNT(*) ---------- 650
数据导入成功后就可以根据具体的问题现在做近一步的分析。
其实导出和导入的步骤非常简单,Oracle直接给出了步骤,难的是拿到数据后如何使用这些数据进行近一步的分析,从而找出问题的根本原因。
如下分析每个sampletime的会话数量
参考:http://www.eygle.com/archives/2009/08/howto_dump_ashinfo.html
https://antognini.ch/2017/07/offline-analysis-of-ash-data-with-ashdump/