mayitong的个人空间

mayitong的个人空间 http://space.itpub.net/48620 Copyright(C) mayitong的个人空间 SupeSite/X-Space Tue, 14 Oct 2008 14:39:34 GMT vacabulary http://space.itpub.net/48620/viewspace-448510 greasy:oily and salty

artificially:man-made

undercarriage:help the plan to land on safely

aeroflot: Russion civil aviation

]]> blog mayitong Tue, 16 Sep 2008 09:28:25 GMT vacabulary http://space.itpub.net/48620/viewspace-446900 mechanic

scraped

infant

contaminated

]]> blog mayitong Fri, 12 Sep 2008 08:59:47 GMT common wait event http://space.itpub.net/48620/viewspace-445556 db file parallel read :

It has no relation with parallel read and parallel DML,It just appear in that priod when doing recover and some server process read noncontinue oracle blocks within one or more datafiles.

db file parallel...]]> blog mayitong Thu, 11 Sep 2008 15:06:04 GMT vacabulary http://space.itpub.net/48620/viewspace-442858 I will tan that boy

limbs

]]> blog mayitong Wed, 10 Sep 2008 09:13:45 GMT How to pass an exam http://space.itpub.net/48620/viewspace-442420 blog mayitong Mon, 08 Sep 2008 19:00:26 GMT vacabulary http://space.itpub.net/48620/viewspace-442288 I wans under the impression

renovate

as you probably are aware

submarines

symptoms

rescue squad

that was supposed to happen

mortgage(抵押）

giant (巨大的）

avert （防止，...]]> blog mayitong Mon, 08 Sep 2008 09:12:57 GMT my idear of smoking http://space.itpub.net/48620/viewspace-441974 If you take notice in places,you will recognize that most of smokers are young people,even middle school students.It's said in China there are 0.3 bilion people smoking.why do they smoke?some thing smoking makes them look cool and ...]]> blog mayitong Fri, 05 Sep 2008 10:11:14 GMT play computer games http://space.itpub.net/48620/viewspace-441790 As a famous saying 'everything has two sides,advatages and disadvatages.computer games are no exceptions.on the one hand,computer games can stimulate your imagination and arouse your interest in elect...]]> blog mayitong Thu, 04 Sep 2008 10:47:14 GMT stream http://space.itpub.net/48620/viewspace-440587 blog mayitong Tue, 02 Sep 2008 22:01:30 GMT 准备好了两可测试库，准备做downsteam捕获的相关测试 http://space.itpub.net/48620/viewspace-440391 rman 的duplicate target database确实是一个不错的命令，两个数据库很快全部搞定。由于这两个库建立分别建立在rac node的本地硬盘，在创建的时候为了图省事，两个数据库的名字都叫myt1，结果启动的时候报ORA-00304: requested INSTANCE_NUMBER i...]]> blog mayitong Mon, 01 Sep 2008 20:25:42 GMT generation gap http://space.itpub.net/48620/viewspace-439122 Young people are ofen unhapply with their parents.They think their parents don't understand him.they feel that their parents are too strict with them.parents often find it difficult to win the children's trust.

...]]> blog mayitong Mon, 01 Sep 2008 09:30:02 GMT ORACLE 版本升级问题 http://space.itpub.net/48620/viewspace-410285 1.升级时候一定要明确，对于使用analyze table的时候会分析索引信息的，但是dbms_stats不会。

2.oracle 10g method_opt的默认值为for all columns size auto，那么我们可能会得到错误的直方图信息。

blog mayitong Sun, 27 Jul 2008 10:27:27 GMT ORACLE CBO 的工作原理 http://space.itpub.net/48620/viewspace-407195      ORACLE 8I中CBO在获取一个表的选择度的时候，只会去考虑user_tab_col_statistics.num_distinct的值去生成COST，而对于ORACLE 9I和10g，如果没有histogram则使用rows/num_distinct生成cost，如果有histogram则使用num_row*densit...]]> blog mayitong Wed, 23 Jul 2008 16:02:09 GMT English(morning) http://space.itpub.net/48620/viewspace-406782 Mark and Helen run import-export company.

she has decided to investigate the benefits of sea cargo over air freight.

I was under the impression that your father never wanted his cargo to go by ...]]> blog mayitong Tue, 22 Jul 2008 09:25:04 GMT flash back在ORACLE 数据库中的使用 http://space.itpub.net/48620/viewspace-406722       ORACLE 9I中的flash back完全依赖于AUM，而且对于drop 以及truncate 等操作也是无能为力的，并且受到回滚表空间大小的限制，能够闪回的时间也是有限制的。一般的语法为：select * from table_name as of timestamp to_tim...]]> blog mayitong Mon, 21 Jul 2008 22:25:35 GMT 2007-07-21(morning) http://space.itpub.net/48620/viewspace-405478 Buying a new car is not a easy task,especially you have a old car to trade in.

Doug stuck the deal with the sales man.

Recently I noticed my furniture looked torn and shabby<...]]> blog mayitong Mon, 21 Jul 2008 10:00:52 GMT 数据迁移的几种方法以及适用的场合 http://space.itpub.net/48620/viewspace-402549       对于一个可以长时间停库的OTLP数据库来说，可以简单的采用exp/imp方式，但是由于imp的速度是很慢的，不过不是跨平台、跨版本的数据库迁移，也可以考虑采用TTS来进行，该方式比imp稍有进步，但在CP 数据文件并FTP数据文件的时...]]> blog mayitong Wed, 16 Jul 2008 22:31:57 GMT English Corner 2008-07-16 http://space.itpub.net/48620/viewspace-402188     He is a hero of Indian,who is favotite of nonviolence,fight againt BITISH rule.he is a saint and be stict with himself and he take great pains to build up a independent country.Especially when h...]]> blog mayitong Wed, 16 Jul 2008 21:31:56 GMT 数据库SQL语句优化的方法论 http://space.itpub.net/48620/viewspace-401720       一般对于一个索引方式访问表数据库块的时候，一般会有4个逻辑读，从root-->branch-->leaf--->rowid。对于更新很少列上的多列查询，可以尽可能采用符合索引的方式，以便省去回表的逻辑I/O。在一个OLTP的数据库中一...]]> blog mayitong Tue, 15 Jul 2008 22:37:09 GMT 高可用性环境中的并发性 http://space.itpub.net/48620/viewspace-401598       在一个繁忙的OLTP数据库中，最重要的特性莫过于并发性和一致性的控制。它的实现主要是靠lock来实现的，通常意义的lock包括如下几种：

     TM LOCK，这种lock在大多数情...]]> blog mayitong Mon, 14 Jul 2008 22:01:45 GMT 在高并发和高负载环境下的数据维护 http://space.itpub.net/48620/viewspace-400044         有的时候在数据维护的时候，往往会导致一些非常严重的逻辑性错误，例如避免丢失更新，千万不要认为update中a.userid=b.userid就万事大吉。如果一定要用游标方式来进行更新，切记使用临时...]]> blog mayitong Sun, 13 Jul 2008 22:58:36 GMT DMT到LMT 转变过程中ORACLE 内部所执行的操作。 http://space.itpub.net/48620/viewspace-399607 今天做一个数据库的优化项目，主要是清理业务产生的垃圾数据，在优化的过程中，发现很多要清理的表都落在了DMT上了，应此在truncate 一些业务表的时候，导致了enqueue ST的所，于是就想到了：使用dbms_space_admin.tablespace_migrate_to_local这个存储过...]]> blog mayitong Sat, 12 Jul 2008 23:38:42 GMT 关于OLTP数据库和OLAP数据库设计应该考虑的问题 http://space.itpub.net/48620/viewspace-375006      OLTP数据库瓶颈主要表现在逻辑读总量和计算性函数上面，因为在该类系统上大部分都是执行的比较频繁的小的业务语句，因此此时cache的使用就显的尤为重要，另外大量的db file sequrntial read对存储系统的IOPS将是一个非常关键的因...]]> blog mayitong Fri, 11 Jul 2008 12:22:00 GMT ORACLE TTS的使用 http://space.itpub.net/48620/viewspace-374598        ORACLE 的TTS主要用在OLTP数据库向OLAP数据库快速传递数据，并且可以用在将中心数据库中的数据发布到其他较小的数据库中，具体步骤如下：

      1.检查源和目...]]> blog mayitong Tue, 08 Jul 2008 19:16:56 GMT English Corner 2008-07-07 http://space.itpub.net/48620/viewspace-374504 unusual function:

pink pig

skiping rope

red beans

magic cup

]]> blog mayitong Tue, 08 Jul 2008 13:37:08 GMT oracle ASM磁盘组的一些特性。 http://space.itpub.net/48620/viewspace-374411           ASM 磁盘组对于数据文件来说，每个extent为1M，对于日志文件和控制文件来说是128K。在ASM环境中对于冗余方式为external的数据文件的大小最大为300G（非bigfile表空间）。ASM具有与生俱来的平衡I/...]]> blog mayitong Mon, 07 Jul 2008 19:31:18 GMT English Corner 2008-07-07 http://space.itpub.net/48620/viewspace-374319 KUFU PANDA

yesterday is history,tomorrow is mysterios,but today is gift.

private space

]]> blog mayitong Mon, 07 Jul 2008 12:33:54 GMT English New Words http://space.itpub.net/48620/viewspace-374271 and it' s more spacious!

she has quite good reputation in her field.

he leads a faily normal life.

he graduated with bachelor degree of comp...]]> blog mayitong Mon, 07 Jul 2008 08:05:20 GMT 开博的大喜日子，先自己庆祝一下！！ http://space.itpub.net/48620/viewspace-374242      很久以前就想开博，但是自己总是以这样或者那样的借口为自己开脱，所以这个愿望始终没能实现。现在正式下定决心做了，希望能坚持做好，本空间主要涉及的是ORACLE 数据库维护和主机存储方面的知识的一些个人心得。]]> blog mayitong Sun, 06 Jul 2008 14:13:26 GMT