Louis workspace – Page 15

Incremental Statistics for Partitioned Tables in 11g

Updated on December 22, 2014 by Louis Liu

这篇文档是我们前leader wwf 写的分析文档,指出了incremental statistic针对partition table 的一些用法,并且指出了一些bug,看不了slideshare的TX可以直接下载Inc_Stat_For_PT.doc

Incremental statistics for partitioned tables in 11 g from Louis liu

针对这几个bug问题在11gR2下的表现对这篇文档做了一个补充

第一个问题:It is only sensitive for newly load data[……]

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Logon Storm

Updated on December 22, 2014 by Louis Liu

A Logon storm is a sudden spike in the number of client connection requests. Logon storms can occur due to a variety of factors. They could be malicious like a DoS attack. Or they could occur due to administrative actions – such as a middle tier coming online.
The process of starting a database[……]

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Oracle latch internals

Updated on December 22, 2014 by Louis Liu

Oracle latch internals

Server latch implementation called KSL, e.g. every table with name starting with x$ksl… is latch
related and every SGA has ksl… structure as well. In order to get complete list of x$ksl table,
connect with sysdba permissions to oracle and run query:

SELEC[……]

some change in cache buffer handle

Updated on December 22, 2014 by Louis Liu

今天开发因为连接数不够强烈要求加大processes值,突然想到了processes对_cursor_db_buffers_pinned的影响,,小记之:

当会话需要pin住buffer header时它首先要获去buffer handle,实例所存在的buffer handle总数由(each process can cache buffer handles*processes决定),也就是说在10g中可以认为 total buffer handle (_db_handles)=5*processes(默认_db_handles_cached为5）,而在11g中这个值发生了变化(in[……]

Bitmap index tips

Updated on December 22, 2014 by Louis Liu

对于BITMAP index的使用一直存在一些争议我们来看看下面几个观点：

1. Low cardinality – Some dabase vendor, like Oracle, provides very practical suggestion

If the number of distinct values of a column is less than 1% of the number of rows in the table, or if the values in a column are repeated more than 100 times,[……]

互联网那点事

Updated on December 22, 2014 by Louis Liu

Facebook最近大热,高调的上市伴随着一路的低走,不少人为之疯狂疑虑、困惑这个里程碑式的公司到底怎么了.在这里小感慨下 facebook还是那个facebook 他一直没有变也许在没上市之前大家只是看到了他光鲜的一面。
其实为什么突然想到这个问题呢不外乎最近公司近乎疯狂的邮件轰炸.内容不外乎于别人facebook是怎么解决这个问题的，别人facebook的架构是怎么样的。也许这些想法本身并没有错 facebook google这些公司是站在了互联网技术的最高端导致一些人的异想天开（依葫芦画瓢？）nosql还没怎么接触就开始讨论HBASE、Cassandra 大数据方[……]

Why ASM?

Updated on December 22, 2014 by Louis Liu

Why ASM?

. ASM is an Oracle provided Database/Cluster filesystem and Storage Volume manager, optimized for Oracle for any kind of workload (be it OLTP or DSS or Batch, sequential or random access), built-in with the database, with no additional cost.

. It follows SAME (Stripe and Mi[……]

Scripts: check user all granted privileges

Updated on December 22, 2014 by Louis Liu

this scripts is used to check user all privileges

set serveroutput on;
DECLARE
v_user VARCHAR2(30) := ‘XXX’;
v_ddl VARCHAR2(2000);
v_status VARCHAR2(32);
BEGIN
— Need to add the following to get the lines to end with semi-colons

dbms_metada[……]