zoukankan      html  css  js  c++  java
  • enq: US contention等待事件

    This event indicates the session is currently waiting on the Undo Segments and is often related to using system managed undo with an auto tuned undo retention period. In 10g, Oracle added the _undo_autotune parameter which allows the database instance to extend and override "UNDO_RETENTION" settings. This is especically true when the datafiles for the Undo Tablespace are set to automatically extend. However, there are limitations and issues with this feature discussed in more detail in the Solutions section below. Here are more details about Automatic Tuning of Undo. Solutions Review Bug 7291739 which affected Oracle 10.2.0.4 and is fixed in 10.2.0.4.4 / 10.2.0.5 and 11.2. It is caused by runaway queries inflating the undo retention time. This fix allows users to specify a high threshold for undo retention via the "_highthreshold_undoretention" parameter. The tuned value of undo retention will then not exceed the set value. Ensure the UNDO tablespace has enough space and/or can autoextend to accomodate the undo settings. If all else fails or you cannot install the latest patchset, disable automatic undo tuning by setting "_undo_autotune" = false.
  • 相关阅读:
    node03
    node02
    node01
    Vue-router重修02
    Vue-router重修01
    Vue重修02
    VUE重修01
    利用表达式目录树进行实体映射
    C#托管堆和垃圾回收
    C# 异步锁
  • 原文地址:https://www.cnblogs.com/macleanoracle/p/2967900.html
Copyright © 2011-2022 走看看