cursor: pin S wait on X 分析

从oracle10g(10.2.0.2)开始 ,开始启用mutex来替换以前的library cache bin latch,这是一种os级更低层的轻量级锁,但是也不是那么完美,有时会出现events cursor: pin S wait on X

ASMLib and OCFS2在RHEL6不再免费支持

Doc ID 1089399.1: ”For RHEL6 Oracle will only provide ASMLib software and updates via Unbreakable Linux Network(ULN). Oracle will no longer provide ASMLib packages for Red Hat kernels.”

How do you know empty block? dump block

看老白日记中有一个案例提到有一个select from where rownum<10的查询要很长时间,后来做了block dump断定是碎片,但是dump出来的内容是如何判断都是空块的呢?

bulk collect 会不会引发not data found?

The FETCH statement never raises a NO_DATA_FOUND exception as it is anticipated that it will eventually hit this condition ,Because the processing of the BULK COLLECT INTO clause is similar to a FETCH loop

alter table move 遭遇ORA-01652: unable to extend temp segment

anbob@ORCL> alter table testspace move tablespace anbob;
alter table testspace move tablespace anbob
ERROR at line 1:
ORA-01652: unable to extend temp segment by 128 in tablespace ANBOB

truncate table 会不会释放datafile的空间?如何才能释放?

下面我将做一这一实验来证明 oracle 10g r2 system@ORCL> create tablesp […]

安装gc遭遇oui-25031 web cache configuration assistant faild!

环境linux rhel 5 , grid constol 102011 问题 oui-25031:some […]

最近好累

时间过的真快,马上又一年,感觉好累好累…

ORA-01877: string is too long for internal buffer 排查

SQL> select BUILD_DATE,dump(build_date) from jmjk_jilin_th_mhk.ehealth_arch_basicinfo where BUILD_DATe>sysdate
2 ;
ERROR:
ORA-01877: string is too long for internal buffer

mysql 快速复制数据库

MyIsam 引擎复制相对容易,把库下面所有文件拷过去就好了。复制Innodb的做法相对复杂,下面是我在innodb 上复制数据库的方法,用mysqldump

where is null 走索引

普通了b树索引是对null不可能走索引的,不讨论cluster table,但是可以通过建立复合索引来使where is null 走索引,

What is “save undo”?

save undo is undo saved for offlined tablespaces. It is also known as deferred rollback

如何看待sql执行计划里的cost

cost 内部记算方法oracle也不会公开,oracle内部用来比较各个执行计划所耗费的代价的值,从而使优化器可以选择最好的执行计划。不同语句的cost值不具有可比性,只能对同一个语句的不同执行计划的cost值进行比较。

trace create user command, who is _next_user?

接着上一篇的问题,再来分析一下用户表,用10046跟踪一下create user

drop tablespace ORA-01561案例

今天遇到了一个奇怪的问题,有一个表空间无法删除,开始删除提示表空间内有对象,加上INCLUDING CONTENTS选项级连删除又报
ORA-01561: failed to remove all objects in the tablespace specified,查一些系统视图该对象还不存在

events errorstack 分析job失败一例

早接到电话说从sqlserver同步过来的数据在oracle 应用没查到,我查询同步job发现失败了,job所调用的procedure 生成了错误编号ORA-02291
procedre中代码较多,决定用errorstack快速定位一下sql