Oracle Database Tuning ADDM
ADDM (Automatic Database Diagnostic Monitor) implements the Oracle performance method and analyzes statistics to provide automatic diagnosis of major performance problems. Because ADDM can significantly shorten the time required to improve the performance of a system, it is one of the most used performance tuning tools of Oracle database.
1. Run some operations on your database instance.
First, start your database instance and do the database operations (select, update, delete...) which will be optimized. e.g. run a script to make some queries in database:
sh run.sh -r rdf1mm-performance -t p -f p3.txt
2. Login to EM
Login to Database EM home page (https://:5500/em), click Performance tab.
3. Run ADDM
Click Button "Run ADDM Now", and click "Yes" on the confirmation page. After a while, we will see the ADDM analysis page.
Database Activity chart shows the database activity during the ADDM analysis period.
In the ADDM Performance Analysis table, ADDM findings are listed in descending order, from highest to least impact. The Informational Findings section lists areas that have no performance impact and are for information only.
4. Implement ADDM recommendations
Click the ADDM findings that has the impact on performance. e.g. Top SQL Statements.
The Category column displays the category of recommendation. The Benefit column displays the estimated benefit of implementing the recommendation.
If we click "Run Advisor Now", SQL tuning advisor will give us some recommendations on how to tune the SQLs.
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在利用NETWORK_LINK方式导出的时候，出现了这个错误。
详细错误信息如下：
bash-3.00$ expdp yangtk/yangtk directory=d_temp dumpfile=jiangsu.dp network_link=test113 logfile=jiangsu.log tables=cat_org
Export: Release11.1.0.6.0 - 64bit Production on星期二, 16 9月, 2008 17:08:22
Copyright (c) 2003, 2007, ......
Checking kernel parameters
Checking for semmsl=250; found semmsl=250. Passed
Checking for semmns=32000; found semmns=32000. Passed
Checking for semopm=100; found semopm=32. Failed <<<<
Checking for semmni=128; found semmni=128.&nb ......
（一）什么叫用户（user）：
A user is a name defined in the database that can connect to and access objects.
用户是用连接数据库和访问数据库对象的。（用户是用来连接数据库访问数据库）。
（二）什么叫模式(schema)：
A schema is a collection of database objects (used by a user.).
Schema objects are th ......
很不幸，建立的表被某人误删了，，，
还好可以通过这样恢复。
select * from user_recyclebin where original_name like 'FINANCE_%' order by droptime desc;
FLASHBACK TABLE FINANCE_CASE_FEE_ITEM TO BEFORE DROP
即所有drop的表都在 user_recyclebin 这个oracle回收站里面的，再通过flashback命 ......
Oracle 中的树查询和 connect by
使用 connect by 和 start with 来建立类似于树的报表并不难，只要遵循以下基本原则即可：
使用 connect by 时各子句的顺序应为：
select
from
where
start with
connect by
order by
prior 使报表的顺序为从根到叶（如果 prior 列是父辈）或从叶到根（如果 prior 列是后代）。
......
