Analyzing 'enq: HW - contention' Wait Event (Doc ID 740075.1) In this Document   Symptoms   Cause   Solution   References APPLIES TO: Oracle Database Cloud Schema Service - Version N/A and laterOracle Database Exadata Cloud Machine - Version N/A and…

今天生成了生产库前几日的AWR报告,发现等待事件中出现了一个陌生的event--enq: HW - contention,google一下是ASSM(Auto Segment Space Management)的表空间上扩展时引起的等待.通常是有LOB大对象的表的并发插入.更新引起的LOB Segment High Water Mark并发争用:了解了之后开始解决问题. 原因:为防止多个进程同时修改HWM而提供的锁称为HW锁.想要移动HWM的进程必须获得HW锁.若在获取HW锁过程中发生争用,则等…

Undo Related Wait Events & Known Issues (Doc ID 1575701.1) APPLIES TO: Oracle Database - Enterprise Edition - Version 9.2.0.8 to 11.2.0.4 [Release 9.2 to 11.2]Oracle Database Cloud Schema Service - Version N/A and laterOracle Database Exadata Express…

1.1问题现象  应用反馈业务执行SQL响应超时,需要数据库排除DB是否存在问题,创建AWR观察到top event 新增enq: US - contention  ??? 1.2问题分析 1) DB Time指标 2020-11-12 17:30 18:00 DB time 3310.19 2020-11-12 18:00 18:30 DB time 15883.77 2020-11-12 18:30 19:00 DB time 19463.52 2020-11-12 19:00 19:30…

最近使用物化视图同步的环境在大量刷新的时候频繁出现enq: JI – contention等待事件,经查: JI enqueue is acquired in exclusive mode on the mview base (container) table when more than one session refresh the same materialzed view. It ensures that two or more refresh processes do not try…

[故障处理]队列等待之enq IV -  contention案例 1.1  BLOG文档结构图 1.2  前言部分 1.2.1  导读和注意事项 各位技术爱好者,看完本文后,你可以掌握如下的技能,也可以学到一些其它你所不知道的知识,~O(∩_∩)O~: ① 队列等待之enq IV -  contention案例(重点) Tips: ① 本文在itpub(http://blog.itpub.net/26736162).博客园(http://www.cnblogs.com/lhrbest)和微信公…

Doc ID 1476663.1) To Bottom In this Document   Purpose   Troubleshooting Steps   Brief Definition:   Problem Confirmation:   Library Cache Pin   Cursor Pin S wait on X   Improving Performance of Library cache pin or Pin S wait on X   Measuring Succes…

Copyright (c) 2019, Oracle. All rights reserved. Oracle Confidential.     ORA-4031 错误故障排除与诊断[视频] (Doc ID 2016002.1) To Bottom 文档内容   用途   常见 Bug   问题和答案   在 SGA 池中内存是如何分配和释放的?   什么是子池(Subpools)?   什么是保留区域?   SGA 中的各池的作用是什么?   ORA-4031 错误是什么?   我的保留区域…

Copyright (c) 2018, Oracle. All rights reserved. Oracle Confidential. Click to add to Favorites Troubleshooting: High Version Count Issues (Doc ID 296377.1) To BottomTo Bottom In this DocumentPurpose Ask Questions, Get Help, And Share Your Experience…

Troubleshooting 'enq: FB - contention' Format Block Enqueues. (Doc ID 1379986.1) In this DocumentPurposeDetails If this wait appears in the Top 5 waits, one can look to implement the following:ReferencesAPPLIES TO:Oracle Database - Enterprise Edition…

Troubleshooting ORA-1628 - max # extents (32765) reached for rollback segment <SEGMENT_NAME> (Doc ID 1580182.1) APPLIES TO: Oracle Database Cloud Schema Service - Version N/A and laterOracle Database Exadata Cloud Machine - Version N/A and laterOrac…

SRDC - ORA-22924 or ORA-1555 on LOB data: Checklist of Evidence to Supply (Doc ID 1682707.1) Action Plan 1. Check for LOB Corruption usingsrdc_corrupt_LOB.sql script. Collect the spool output.  脚本检查LOB损坏 --srdc_corrupt_LOB.sql REM srdc_corrupt_LOB.sq…

[故障解决]enq: PS - contention 一.1  BLOG文档结构图       一.2  前言部分   一.2.1  导读和注意事项 各位技术爱好者,看完本文后,你可以掌握如下的技能,也可以学到一些其它你所不知道的知识,~O(∩_∩)O~: ① 等待事件 enq: PS - contention的解决办法 ② 一般等待事件的解决办法     Tips:        ① 若文章代码格式有错乱,推荐使用QQ或360浏览器,也可以下载pdf格式的文档来查看,pdf文档下载地址:htt…

Outer Join Query Over Dblink Can Fail With ORA-904 (Doc ID 730256.1) To Bottom Modified:03-May-2013Type:PROBLEM In this Document   Symptoms   Changes   Cause   Solution   References APPLIES TO: Oracle Database - Enterprise Edition - Version 10.2.0.1…

[等待事件]序列等待事件总结(enq: SQ - contention.row cache lock.DFS lock handle和enq: SV -  contention) 1  BLOG文档结构图 2  前言部分 2.1  导读和注意事项 各位技术爱好者,看完本文后,你可以掌握如下的技能,也可以学到一些其它你所不知道的知识,~O(∩_∩)O~: ① 序列等待事件总结 ② enq: SQ - contention.row cache lock.DFS lock handle和enq: SV…

--每分钟操作 SQL> select  sql_id, mi, count(mi)   2    from (select event, sql_id, to_char(sample_time, 'yyyymmdd hh24mi') mi --,   3          --session_id   4            from dba_hist_active_sess_history   5           where sql_id = '7wxfw53bsmgpq'   6  …

今天下午,有台服务器出现异常,响应特别慢,io等待奇高,awr top 5事件如下: 经回查ash,找到了造成这些事件的sql语句,如下: select * from v$active_session_history where event='enq: TM - contention' select * from v$active_session_history where event='enq: KO - fast object checkpoint' enq-TM的事件主要由insert /…

这几天遇到一个错误,我也不知道算不算错误吧,因为没有报错,只是在那突然的短短2分钟内表的操作突然降低了,导致了该软件重新启动.查看alert日志没有报错,而是在ASH里找到了TOP SQL框有一个这样的错误,使我百思不得其解.查看该SQL语句只是简单的一个更新,并不需要优化.最后再百度.google的帮助下终于找到了错误原因,原来与UNDO的设置有关.首先来介绍下undo_retention参数,该参数是撤销段的最短保留时间,而在默认情况下Oracle将根据表空间的大小和历史使用情况,自动调整u…

Test Case:: 12C ASM New feature (Doc ID 1571975.1) APPLIES TO: Oracle Database - Enterprise Edition - Version 12.1.0.1 and laterInformation in this document applies to any platform. PURPOSE This document is a discussion of a few 12C ASM new features…

Test Case:: 12C ASMCMD New feature (Doc ID 1589249.1) APPLIES TO: Oracle Database - Enterprise Edition - Version 12.1.0.1 and laterInformation in this document applies to any platform. PURPOSE There are a few new features at asmcmd level that have be…

11.2 Data Guard Physical Standby Switchover Best Practices using SQL*Plus (Doc ID 1304939.1) APPLIES TO: Oracle Database - Enterprise Edition - Version 11.2.0.1 and laterOracle Database Cloud Schema Service - Version N/A and laterOracle Database Exad…

LogMiner Utility Release 8i - 11g (Doc ID 291686.1) APPLIES TO: Oracle Database Exadata Cloud Machine - Version N/A and laterOracle Cloud Infrastructure - Database Service - Version N/A and laterOracle Database Exadata Express Cloud Service - Version…

Automatic Tuning of Undo Retention Common Issues (Doc ID 1579779.1) APPLIES TO: Oracle Database - Enterprise Edition - Version 12.1.0.2 to 12.1.0.2 [Release 12.1]Oracle Database - Enterprise Edition - Version 10.2.0.1 to 11.2.0.4 [Release 10.2 to 11.…

FAQ – Automatic Undo Management (AUM) / System Managed Undo (SMU) (Doc ID 461480.1) APPLIES TO: Oracle Database - Enterprise Edition - Version 9.0.1.4 to 18.3.0.0.0 [Release 9.0.1 to 18]Oracle Database Cloud Schema Service - Version N/A and laterOrac…

APPLIES TO: Oracle Database Cloud Schema Service - Version N/A and laterOracle Database Exadata Cloud Machine - Version N/A and laterOracle Database Exadata Express Cloud Service - Version N/A and laterOracle Cloud Infrastructure - Database Service -…

SRDC - ORA-1555 during Export: Checklist of Evidence to Supply (Doc ID 1682706.1) Action Plan 1. Execute srdc_db_undo_1555-1.sql as sysdba and collect the spool output.  以sysdba身份执行 --srdc_db_undo_1555-1.sql REM srdc_db_undo_1555-1.sql REM collect co…

Troubleshooting ORA-01555/ORA-01628/ORA-30036 During Export and Import (Doc ID 1579437.1) APPLIES TO: Oracle Database - Enterprise Edition - Version 9.2.0.1 to 11.2.0.4 [Release 9.2 to 11.2]Information in this document applies to any platform. PURPOS…

SRDC - ORA-1555: Query Duration 0: Checklist of Evidence to Supply (Doc ID 1682704.1) Action Plan 1. Execute srdc_db_undo_1555-1.sql as sysdba and provide the spool output DB_Undo_1555-1.html  以sysdba的身份执行 --srdc_db_undo_1555-1.sql REM srdc_db_undo_1…

Troubleshooting Guide (TSG) - ORA-01552: Cannot Use System Rollback Segment for Non-System Tablespace (Doc ID 1579215.1) APPLIES TO: Oracle Database - Enterprise Edition - Version 9.2.0.1 and laterOracle Database Cloud Schema Service - Version N/A an…

Oracle 性能之 Enq: CF - contention Table of Contents 1. 原因 2. 解决问题 2.1. 针对持有锁进程类型处理 2.1.1. 查看持有锁会话的进程类型 2.1.2. 根据进程类型采取不同的处理方法 2.2. 检查归档路径 3. 总结 1 原因 只要是需要读控制文件的操作期间,都调用并持有 CF enqueue, CF 块用于控制文件相关事务的序列化 操作和在控制文件共享部分的读写操作. 一般来说,控制文件的CF enqueue 锁的申请和持有时间…