zoukankan      html  css  js  c++  java
  • 分析Oracle Mutex等待事件

    Troubleshooting or analyzing waits on mutex events, i.e. ones that start with "cursor:", are very similar to each other and below are some guidelines. There are many bugs related to problems using mutexes in Oracle 10g, the first version where mutexes were introduced. If you are seeing excessive waits on mutexes, a quick fix may be to go back to the library cache latching mechanism. To do this, you can set the parameter _kks_use_mutex_pin=false.   Note: For mutex related waits, v$session.blocking_session is not populated in 10.2. However, v$session.blocking_session is populated in 11g R1.   To do further analysis, the P2RAW column in v$session gives the blocking session, i.e. the holder SID of the mutex in the upper 8 bytes. It is in hex so it needs to be converted in decimal. The following query provides the blockers with the most sessions blocked behind it as well as converts the P2RAW to an usable SID:   select p2raw, to_number(substr(to_char(rawtohex(p2raw)), 1, 8), 'XXXXXXXX') sid, count(1) sessions_waiting from v$session where event = 'cursor: pin S wait on X' group by p2raw, to_number(substr(to_char(rawtohex(p2raw)), 1, 8), 'XXXXXXXX');   P2RAW                      SID    SESSIONS_WAITING ----------------            ---                  ---------------- 0000001F00000000    31                                    79   On 64 bit platforms 8 bytes are used, so the top 4 bytes are the holding session Id (if the mutex is held X), and the bottom 4 bytes are the ref count (if the mutex is held S). On 32 bit platforms 4 bytes are used, so the top 2 bytes are the holding session Id (if the mutex is held X) and the bottom 2 bytes are the ref count (if the mutex is held S).   p1 = The mutex Id This has the same definition as v$mutex_sleep_history.mutex_identifier p2raw = Holding Session Id | Ref Count The most significant bytes always store the Holding Session Id (Holding SID). The least significant bytes always store the Ref Count.
  • 相关阅读:
    Python脚本运行出现语法错误:IndentationError: unindent does not match any outer indentation level
    Python3 运算符
    Python3 注释
    Python3 解释器
    Python3 环境搭建
    Python 3 教程
    Python3 基本数据类型
    趣闻|Python之禅(The Zen of Python)
    ios开发笔记根据传入字符串的长度动态生成label,并按照屏幕宽度排列
    iOS开发设置tableview的分割线
  • 原文地址:https://www.cnblogs.com/macleanoracle/p/2967495.html
Copyright © 2011-2022 走看看