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
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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/
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