04 2013 档案

inode on ext2 ext3 file system
摘要:本文包含以下内容:什么是inodeinode 的内容inode的大小inode作用及如何修改其信息几个命令1. 什么是inode理解inode,要从文件储存说起。文件储存在硬盘上,硬盘的最小存储单位叫做"扇区"(Sector)。每个扇区储存512字节(相当于0.5KB)。操作系统读取硬盘的时候,不会一个个扇区地读取,这样效率太低,而是一次性连续读取多个扇区,即一次性读取一个"块"(block)。这种由多个扇区组成的"块",是文件存取的最小单位。"块"的大小,最常见的是4KB,即连续八个 sector组成一个 blo 阅读全文

posted @ 2013-04-26 15:12 kramer 阅读(433) 评论(0) 推荐(0)

learn plan - linux inode ,debug script, exist in , crontab log
摘要:2013年4月26日14:37:30近期要了解一下以下内容:1. linux inode 2013年4月28日15:44:132. shell script的 debug mode3. oracle exist in4. crontab 的log 阅读 阅读全文

posted @ 2013-04-26 14:40 kramer 阅读(150) 评论(0) 推荐(0)

Reducing Loop Overhead for DML Statements and Queries with Bulk SQL(10gr2)
摘要:PL/SQL运行SQL的机制是把SQL语句,比如DML,SELECT,发送给SQL 引擎。然后SQL引擎把SQL语句的结果返回给PL/SQL。想象一下,下面这样的PL/SQL块。FOR j IN 1..99999999 LOOP VAR1[i]=i; INSERT INTO TEST VALUES(VAR[i]);END LOOP;这个PL/SQL块非常简洁明了,它循环9999999次,每一次循环都把 i 赋值到 VAR1[i]中,然后把这个VAR1[ i ] insert到表TEST中。这么简单的SQL却有着非常严重的性能问题。因为他要循环99999999次,每一次循环PL/SQL引擎都.. 阅读全文

posted @ 2013-04-25 11:33 kramer 阅读(246) 评论(0) 推荐(0)

view optimization (10gr2)
摘要:When talking about view optimization, we need to know about mergeable view and unmergeable view. 10gr2 concept gives very clear definition.The optimizer can merge a view into a referencing query block when the view has one or more base tables, provided the view does not contain:set operators (UNION, 阅读全文

posted @ 2013-04-24 15:29 kramer 阅读(268) 评论(0) 推荐(0)

知道创宇
摘要:Expand - Collapse知道创宇研发技能表v2.1创建时间:2012/12/1更新时间:2013/4/22by @知道创宇(www.knownsec.com) 余弦(新浪:@余弦)说明本技能表为知道创宇研发工程师必备技能聪明的人会根据每个tip进行自驱动扩展不聪明的,坐等别人手把手的人请绕行,不仅不适合知道创宇,也不适合任何有Geek精神的公司附件标志是我们推荐的附加资源,感谢资源提供者知道创宇研发技能表v2.1离线版打包下载 通用技能公司与个人公司是盈利性组织个人和公司必须双赢工作在认同公司理念且能够给公司创造足够价值的基础上,为个人发展而工作沟通、反馈、责任一个无沟通能力的人,要 阅读全文

posted @ 2013-04-24 11:28 kramer 阅读(854) 评论(0) 推荐(0)

Oracle 11gr2 silent install on Solaris 11
摘要:We will not give details on how to do silent installation step by step. Here we just give some key points where you may hit error.1. oracle support accountYou need to specify your oracle support account and password in the response file. If you dont do this, you will hit error when run silent instal 阅读全文

posted @ 2013-04-22 16:29 kramer 阅读(205) 评论(0) 推荐(0)

主键冲突了,语句是不是还会被写入redo?
摘要:考虑这种情况insert into t values (8,'eight');insert into t values(9,'nine');insert into t values(10,'ten');insert into t values(11,'ten');insert into t values(12,'ten');如果上面的语句 有一条发生了类似主键错误,那么我们怎么能知道是哪一条呢。答案。。 通过logminer 可以看到。SQL> SELECT TO_CHAR(TIMESTAMP,'YY 阅读全文

posted @ 2013-04-19 15:53 kramer 阅读(324) 评论(0) 推荐(0)

oracle 11gr2 (11.2.0.3.0) install on Solaris 11
摘要:Operating system versionSunOS s11db11g 5.11 11.0 i86pc i386 i86pcThe issue happened during run oracle universal installer.>>> Ignoring required pre-requisite failures. Continuing...Preparing to launch Oracle Universal Installer from /u04/tmp/OraInstall2013-04-18_11-02-02AM. Please wait ...o 阅读全文

posted @ 2013-04-18 18:37 kramer 阅读(1021) 评论(0) 推荐(0)

Setup X11 forwarding on Solaris11 with putty ans x-ming
摘要:Set up x env on solaris111. latch x-ming in local env2. set up putty in local env3. Login to Solaris11 do belowedit /etc/ssh/sshd_config# X11 tunneling optionsX11Forwarding yesX11DisplayOffset 10X11UseLocalhost yesrestart sshdsvcs -a | grep sshsvcadm restart install xclock to test and xauth to enabl 阅读全文

posted @ 2013-04-17 17:12 kramer 阅读(355) 评论(0) 推荐(0)

SQL Queries and Subqueries(10gR2)
摘要:Before start reading this article, you need to pay attention to the words in red.About Queries and SubqueriesCreating Simple QueriesHierarchical QueriesThe UNION [ALL], INTERSECT, MINUS OperatorsSorting Query ResultsJoinsUsing SubqueriesUnnesting of Nested SubqueriesSelecting from the DUAL TableDist 阅读全文

posted @ 2013-04-15 14:41 kramer 阅读(826) 评论(0) 推荐(0)

转载
摘要:常常有人把这三个hint搞混,主要是因为对三种重写原理不清楚。特总结如下。(实验环境为10204)1. no_unnest, unnestunnest我们称为对子查询展开,顾名思义,就是别让子查询孤单地嵌套(nest)在里面。所以un_unnest双重否定代表肯定,即让子查询不展开,让它嵌套(nest)在里面。现做一个简单的实验:create table hao1 as select * from dba_objects;create table hao2 as select * from dba_objects;analyze table hao1 compute statistics;an 阅读全文

posted @ 2013-04-12 17:05 kramer 阅读(206) 评论(0) 推荐(0)

Unnesting of Nested Subqueries ( 10gr2 )
摘要:本文的目的是要研究一下nested subquery。所谓nested subquery,就是指出现在where语句中用括号括起来的子查询。通常oracle对这些子查询的处理情况是把它们当做一个独立的对象,嵌套在父查询中执行。比如说下面这个例子SQL> select /*+ gather_plan_statistics */ ename from emp where exists (select /*+ no_unnest */ 1 from dept where deptno=emp.deptno and deptno=20);----------------------------- 阅读全文

posted @ 2013-04-12 16:47 kramer 阅读(461) 评论(0) 推荐(0)

IN , EXIST
摘要:在SQL优化中,经常会有人问IN,NOT IN,NOT EXIST, EXIST的区别,会问IN 和 EXIST, NOT IN 和 NOT EXIST做比较哪些会更快些。 以前在RBO时代也许他们还是有区别的,但是现在oracle都是用CBO来处理SQL了,应该不会有区别。 但这只是猜想,还是要试... 阅读全文

posted @ 2013-04-10 15:11 kramer 阅读(353) 评论(0) 推荐(0)

python 导数据脚本
摘要:背景:测试环境有表若干,产品环境有表若干。客户发信要求把产品环境数据同步到测试环境并提供了需要同步的table list。问题:该list可能有如下问题list中的表存在重复list中的表在测试环境不存在list中的表缺少依赖关系,比如parent表不在list中。解决上述问题:list中的表在测试环境不存在的问题:我们先根据客户提供的list,也就是rawlist创建一个外部表create directory my_dir as '/tmp';create table raw_list_tab(owner varchar2(40),table_name varchar2(80 阅读全文

posted @ 2013-04-09 18:08 kramer 阅读(317) 评论(0) 推荐(0)

v$ view and v_$ view
摘要:不知道我是太较真了还是太闲了,才会写下这篇文章。本文主要讨论一下 V$ 和 V_$开头的这些数据对象的关系。 通常来说他们的关系是这样的V$开头的一般来说是同义词,他们通常指向同名的V_$视图,或者指向同名的V$ fixed view。比如 这是上图的前三层。它们都只反映了单实例的一些信息,所以它们一般是从GV这种数据对象中根据instance id 截取出来的,也就是后面的4-6层。GV$开头的一般也是同义词,通常指向GV_$这样的视图或者指向同名的GV$ fixed view。这是4-6层。而第七层是最底层是X$ 开头的fixed table。 他们是最底层的,上面6层的信息一般是从这一层 阅读全文

posted @ 2013-04-09 12:45 kramer 阅读(368) 评论(0) 推荐(0)

cache buffers chains
摘要:cache buffers chains 看名字像是一个链表结构,但实际上它是一个latch。 要理解它,首先要理解下面的概念。hash buckethash chain listhash bucket和hash chain list是用来在data buffer里快速定位数据块的。oracle在访... 阅读全文

posted @ 2013-04-08 16:41 kramer 阅读(827) 评论(0) 推荐(0)

automount
摘要:Automoun is another kind of NFS. The different is that in NFS mode the client need to connect to NFS server all the time. This will consume server resources making the server slow. But in automount mode, client dont have to connect to server all the time. When you access the nfs resource, the automo 阅读全文

posted @ 2013-04-08 11:50 kramer 阅读(280) 评论(0) 推荐(0)

Never use absolute path when you create tar
摘要:In unix, especially Solaris, the tar file is dangerous if you create a tar file with absolute path.For example:We have an very important config files here, if you change the content may cause some problem1 bash-2.03$ ls -ltr /home/limingwei/config.txt2 -rw-r--r-- 1 limingwei mqm 3 Apr ... 阅读全文

posted @ 2013-04-02 14:59 kramer 阅读(271) 评论(0) 推荐(0)

Oracle RAC 10g – Cache Fusion(original link is under the title)
摘要:Oracle RAC 10g – CacheFusion8(http://avdeo.com/2008/07/21/oracle-rac-10g-cache-fusion/)Introduction:This post is about Oracle Cache Fusion technology, which is implemented in Oracle database 10g RAC. We are going to discuss just about cache fusion. You should have the architecture knowledge about RA 阅读全文

posted @ 2013-04-01 18:17 kramer 阅读(349) 评论(0) 推荐(0)

where is the data come from after we drop the table
摘要:When I was reading a oracle document, it said that the select action will not put any locks on the table you are reading. That is different from what I thought before. I understand that if a table were selecting, the session will not put any locks to stop othere sesssion from writing the table. Or I 阅读全文

posted @ 2013-04-01 16:33 kramer 阅读(248) 评论(0) 推荐(0)

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