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oracle备库延时的监控方法[@more@]根据最后一个已经apply的日志文件的next_time时间戳进行判断 select /*+ rule */ nvl(round((sysdate-max(NEXT_TIME))*24),999) from v$archived_log where APPLIED！='NO' and REGISTRAR='RFS' http://docs.oracle.com/cd/E11882_01/server.112/e25513/dynviews_1016.htm#REFRN30011 其他检查方式 1.根据system表空间文件的chkpoint时间检查 select /*+ rule */ nvl(round((sysdate-CHECKPOINT_TIME)*24),999) from v$datafile where file#=1; 2.根据最后一个apply的归档文件的创建时间判断，优点是不需

预警的些想法[@more@]1.预警的意义 通知我们某个点出现了异常，并且这个异常在可预见的未来可能会造成什么样的影响2.预警的要素 监控点&触发点&对象&渠道&频率3.一次通知定义 语音外呼-1次，短信-2条，邮件1条，旺旺1条4.常规预警分级 根据影响可能发生的时间和可能造成的影响和评估，而不是简单根据触发点的重要程度 分级的目的1） 重要性的传递2）抑制告警 分级的出发点，主要的级别为LV0，LV1，LV4，LV5。LV2,LV3的预警希望只是用做辅助性分级。 负载类：LV0，LV1，LV4，LV5 负载类告警一般突发性比较强，以短期型

Bug 9290526 - Poor plan for recursive SQL used for DML involving a UNIQUE constraint [ID 9290526.8] … [@more@] A suboptimal plan may be seen for the specific recursive SQL: select c.name, u.name from con$ c, cdef$ cd, user$ u where c.con# = cd.con# and cd.enabled =:1 and c.owner# = u.user#; This can cause inserts involving a unique constraint to show poor performance. Workaround Set optimizer_mode=rule for the affected DMLs. https://supporthtml.oracle.com/epmos/faces/ui/km/SearchDocDisplay.js

softer soft parse 软软解析[@more@]不解释，帖链接http://docs.oracle.com/cd/E11882_01/server.112/e25513/initparams228.htmhttp://docs.oracle.com/cd/E11882_01/server.112/e25513/stats002.htmhttp://www.orafaq.com/node/758http://www.orafan.net/blog/180.html

numa oracle oom[@more@]3.NUMA+oracle的一些问题 1）.rh54-hugepage oracle的sga并非完全预分配，hugepage应该是预分配出page的，虽然没有划给SGA，所以内存分配上应该不会导致问题。另外，hugepage实际分配的大多数位于node1，pagecache位于node0，虽然整体较为平均，不确定是否会有影响，不过个人偏向于影响不大。 2）.numa 进程倾向总是从同一node分配内存，对于oracle，由于使用filecache的进程以arch进程为主，且大部分时候oracle只有一个arch进程工作，可能导致filecache过分集中到一个node里面。 3）.numa

oracle11.2.0.2 dg vcs ha 切换异常[@more@]现象：oracle11.2.0.2+vcs，当有主库的public进程连接到备库时，ha无法正常完成备库实例的切换。问题关键点如下： 1）oracle11.2.0.2 shutdown immediate操作中，会等待active call状态的进程，（不确定是会等待所有处于active call状态的进程还是单单active call状态的RFS进程）；并且这个等待可能是没有超时或者超时设置相当长（从测试中看超过1h）。shutdown操作会一直卡在ipcs看到的第一个信号量（释放？）处，对应系统调用一直在报超时错误。 2）当监听器所侦听的网络异常（这里是IP被

http://dev.mysql.com/doc/refman/5.1/en/replication-options-slave.html#sysvar_slave_exec_mode[@more@]一直都习惯使用slave_skip_errors来忽略类似键值冲突和找不到键错误，偶然发现原来mysql里面竟然有这么一个参数，而且可以动态修改，当然由于未曾在生产环境使用过，还是要谨慎对待之。http://dev.mysql.com/doc/refman/5.1/en/replication-options-slave.html#sysvar_slave_exec_mode

Bug 8575528 Missing entries in V$MUTEX_SLEEP.location[@more@]Affects:Product (Component)Oracle Server (Rdbms) Range of versions believed to be affectedVersions >= 10.2.0.4 but BELOW 10.2.0.5 Versions confirmed as being affected(None Specified) Platforms affectedGeneric (all / most platforms affected) DescriptionThis problem is caused by the fix for bug 6795880. Null mutex locations may be seen in V$MUTEX_SLEEP or a core dump encountered in a call from kqlfMutexClnFetch() to strcpy().

install mysql558[@more@]首先阅读下官方文档说明http://dev.mysql.com/doc/refman/5.5/en/source-installation.html按照cmake吧，就不说了,下载源码，改bughttp://bugs.mysql.com/bug.php?id=58350http://lists.mysql.com/commits/126782编译CC='/usr/bin/gcc' CFLAGS='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -fPIC -Wall -O3 -g -static-libgcc -fno-omit-frame-pointer -fno-strict-aliasing -DDBUG_OFF' CXX='/usr/bin/gcc' CXXFLAGS='-O2 -

blob bug[@more@]http://www.mysqlperformanceblog.com/2010/11/29/data-corruption-drbd-and-story-of-bug/http://bugs.mysql.com/bug.php?id=55981root@test 06:52:04>CREATE TABLE t4(c1 int,c2 int,c3 MEDIUMBLOB,PRIMARY KEY(c1)) engine=innodb;Query OK, 0 rows affected (0.01 sec)root@test 06:52:05>insert into t4 values(1, 2, REPEAT('b', 54903));Query OK, 1 row affected (0.04 sec)root@test 06:52:12>start transaction;Query OK, 0 rows affected (0.00 sec)root@test 06:52:18>update t4 set c1 = 3;Quer

service_name or sid[@more@]问题起源于itpub一个帖子http://www.itpub.net/thread-1358298-1-1.html，答案呢，通过service_name实现failover和lb自然是一方面，顺便查了下oracle文档相关介绍，还是有些特别的发现的。http://download.oracle.com/docs/cd/B19306_01/network.102/b14213/tnsnames.htm#sthref754.6.4.8 SERVICE_NAMEPurposeUse the SERVICE_NAME parameter to identify the Oracle9i or Oracle8 database service to access. Set the value to a value specified by the SERVICE_NAMES parameter in the initialization par

Oracle SQL performance with database links - dblink[@more@]http://download.oracle.com/docs/cd/B14117_01/server.101/b10752/hintsref.htm#30401https://support.oracle.com/CSP/main/article?cmd=show&type=NOT&doctype=PROBLEM&id=825677.1http://www.dba-oracle.com/t_sql_dblink_performance.htmhttp://jiri.wordpress.com/2009/05/20/queries-across-db-link-and-how-driving_site-hint-does-not-work-for-inserts/http://psoug.org/reference/hints.html

Surge Scalability 2010[@more@]Surge Scalability 2010，值得关注下，转一位speaker的演讲概要在这里，希望有所启发。http://ronaldbradford.com/blog/speaking-at-surge-scalability-2010-2010-07-28/Overview:Some details of the presentation would include:The different types of accessible data (e.g. R/W, R, none) What limits MySQL availability (e.g software upgrades, blocking statements, locking etc)The three components of scalability – Read Scalability/Write Scalability/CachingDesign practices for increa

http://mituzas.lt/2010/06/30/replication/[@more@]http://mituzas.lt/2010/06/30/replication/很是认同，转载下There are few things one is supposed to know about MySQL replication in production, as manual doesn’t always discuss things openly.This is small set of rules and advices I compiled (some apply to statement based replication only, but row based replication may benefit from one or two too):Don’t use MyISAM. Or in fact, don’t use any non-transactional engine, if you care about your data. On

作者: 弦乐之花 | 可以转载, 但必须以超链接形式标明文章原始出处和作者信息及版权声明链接http://shiri512003.itpub.net/post/37713/501173[@more@]5148的发布把innodb plugin带入了1.0.9时代，5147innodb plugin更新到了108版本还是马马虎虎能接受，5148的109版本真是乱来了，大家可以看下109的版本变化，innodb本身没有任何变化嘛。。。http://dev.mysql.com/doc/refman/5.1/en/news-5-1-48.htmlInnoDB Plugin has been upgraded to version 1.0.9. This version is considered of General Availability (GA) quality. InnoDB Plugin C

作者: 弦乐之花 | 可以转载, 但必须以超链接形式标明文章原始出处和作者信息及版权声明链接http://shiri512003.itpub.net/post/37713/501132 [@more@]最近没太关注percona分支的mysql5145以上版本了，（其实也是一直很期待基于5147的percona版出现的）今天偶然发现percona已经是发布了5.1.47-11.0，（oracle已经release了5148版，细细看了release note，没有升级的欲望也是）于是下来测试一把，发现还是有点意思的首先看下configue命令的帮助，比较有趣的percona把builtin版本的编译选项修改成只支持动态编译，plugin则支持动静态编译，刚

ibdata1[@more@]记得之前曾在Pub上看到innodb共享表空间暴涨的案例，自己在实际测试中也遇到多（高并发情况），其中缘由也是知晓一二，今天看到peter的两篇博文进行了详细的描述，简单记录下来备查。http://www.mysqlperformanceblog.com/2010/06/10/purge-thread-spira-of-death/I just wrote a large post on reasons for innodb main tablespace excessive growth and I thought it would make sense to explain briefly of why it is so frequently you have purge not being the problem at all and when out of no where you can se

_optimizer_compute_index_stats[@more@]COMPUTE STATISTICS In earlier releases, you could use this clause to start or stop the collection of statistics on an index. This clause has been deprecated. Oracle Database now automatically collects statistics during index creation and rebuild. This clause is supported for backward compatibility and will not cause errors._optimizer_compute_index_stats

文章收集[@more@]fast paging in the real worldhttp://cafuego.net/2010/05/26/fast-paging-real-worldFixing MySQL group commit http://kristiannielsen.livejournal.com/12254.htmlOn Good Instrumentationhttp://www.mysqlperformanceblog.com/2010/05/31/on-good-instrumentation/

oracle之commit控制[@more@]_lgwr_async_io_wait_for_synccommit_writehttp://download.oracle.com/docs/cd/E11882_01/server.112/e10820/initparams032.htm#REFRN10260http://www.oracle-base.com/articles/10g/Commit_10gR2.phpcommit_waithttp://download.oracle.com/docs/cd/E11882_01/server.112/e10820/initparams031.htm#REFRN10266commit_logginghttp://download.oracle.com/docs/cd/E11882_01/server.112/e10820/initparams029.htm#REFRN10265