June 26, 2012 linux No comments
来自公司SA组的一封邮件
HI All
简单来说Linux kernel低于2.6.18-164且开启NTP服务的server有自动重启的风险
目前我们大多数的server kernel如下
$ uname -a
Linux xen21-vm04 2.6.18-128.1.10.el5.xs5.5.0.51xen #1 SMP Wed Nov 11 08:31:24 EST 2009 x86_64 x86_64 x86_64 GNU/Linux
10.1.0.99上
#chkconfig –list|grep ntp
ntpd 0:[……]
June 20, 2012 oracle, replication No comments dataguard
Recover physical standby database after loss of archive log(2)
上次写过一篇DG丢失归档后的处理过程，总体来说就是使用增量备份覆盖gap数据从而跳过gap的archivelog 这里再阐述另一种情况
[oracle@db61 orcl]$ ora si
SQL*Plus: Release 10.2.0.5.0 – Production on Wed Jun 20 14:35:01 2012
Copyright (c) 1982, 2010, Oracle. All Rights Reserved.
Co[……]
June 18, 2012 11g, oracle No comments 11g
查看数据仓库的awr报告发现以下问题 顺便总结一下之前碰到的一类问题
CPU Time (s)Executions CPU per Exec (s)%TotalElapsed Time (s)%CPU%IO SQL IdSQL ModuleSQL Text
13,664.95121,138.758.9915,656.3587.2811.833a1wvmtvsdvqv
PL/SQL Developer
call pkg_rpt_union.pro_rpt_uni…
10,474.6752,094.936.8914,773.1470.9028.906m[……]
June 14, 2012 maintain, oracle No comments scripts
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[……]
June 13, 2012 oracle, RAC No comments asm
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[……]
June 9, 2012 Architect No comments
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[……]
June 7, 2012 Internals, oracle No comments structure
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,[……]
June 7, 2012 Internals, oracle No comments internal
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[……]
June 6, 2012 Internals, oracle 4 comments internal
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[……]