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在ORACLE ASMM或AMM开启的情况下, 数据库来动态调整其中的各个组件,但是在绑定变量较差的系统中shared pool会慢慢增长但不能自动收缩,操作buffer cache 越来越来小影响性能,需要手动调大db_cache_size的值,来控制sharedpool的增长,在调整db_cache_size的时候经常会出现ORA-02097:parameter cannot be m...

一、        SHARED POOL及ORA-4031错误SHARE POOL利用堆（HEAP)的内存管理方式管理，内存是预先分配的，当某个进程需要分配shared pool的内存的时候，Heap Manager就满足该请求，Heap Manager也和其他ORACLE模块一起工作来回收shared pool的空闲内存。SHARE POOL在物理上由...

shared pool library cache latch 竞争严重的症状如下:sharedpool latch 或者 latch:shared pool 之类的Latch争用高CPU解析时间V$LIBRARYCACHE 中的高reloads多版本的cursors大量的parse call经常发生ORA-04031 错误调优办法:1. ...

 影响优化器的相关因素 1.      Initialization parametersCURSOR_SHARING...

New optimizer version·         Changes to schema and metadatadefinitions·         SQL profile creating自动捕获被开启后系统自动创建并维护执行计划历史记录，执行计划历史包含sql语句,绑定变量,编译环境等,...

 stored outline用来保存标准的sql执行计划,无论环境或统计信息的变化，都将不影响sql的性能。 11g以后stored outline被SQL plan management 代理,oracle建议11g以后将stored outline复制到SQL PlanBaselines1.       创建outline需要的权限CREATE ANY OUTLINE ...

一、        批量提交批量提交特点: 占用较少undo,资源(独占锁,undo)快速释放,执行时间长批量提交适合场景:在线大批量插入,更新,删除数据二、        BULK COLLECT+FORALL性能提升1.通过BULK COLLECT加速查询不管是...

global cache cr request/gc current requestThe session is waiting for all pending lock operations on the lock elements (le) attached to a lock context to complete. The session sits in a loop until all requests are complete, and this wait event is effectively a poll interval while waiting.The event ...

"Log Buffer Space"Wait for space in the log buffer because we are writing into the log buffer faster than lgwr can write it out.Reducing WaitsConsider making the log buffer bigger if it is smallMoving the log files to faster disksIncrease size of redo logs...

常见等待事件---shared poollatch: shared poollatch: library cachelatch: library cache locklatch: library cache pin---事务--Segmentenq: HW – contentionenq: ST – contentionenq: TT – contentionenq: US – contention --redo log file synclog...

Table Access Operations? TABLE ACCESSFULLThe Oracle server reads all blocksup to the high-water mark (HWM).? TABLE ACCESSBY ROWIDThe Oracle server gets blocks that areidentifiedby an index lookup, or by a specified ROWID. Index Access Operations? IND...

latch :cache buffers chains 是block headerlacth 的竞争buffer busy waits 和read byother session 是 buffer block 的竞争(10g以后read by other session从buffer busywaits独立出来)参考http://www.itpub.net/thread-1801066-1-1.htmlOracle 访问数据块的大概步骤:1）依据数据块的地址计算出...

Definition:Versions:7.0 - 10.2 Documentation: 9.0This wait happens when a session wants to access a database block in the buffer cache but it cannot as the buffer is "busy". The two main cas...

This wait event usually occurs when you have tried to dynamically resize a component of the SGA such as the buffer cache.The "buffer exterminate" waits can only happen if part of the buffer cache is b...

Wait event 'asynch descriptor resize' is waited for when the number of asynchronous descriptors reserved inside the OS kernel is being re-adjusted.When the number of asynchronous I/O's submitted ...

--row lock contention 阻塞进程查询select *  from v$session a where a.SID in (select BLOCKING_SESSION                   from v$session m&nbsp...

APPLIES TO:Oracle Server - Enterprise Edition - Version 9.2.0.8 to 11.2.0.3 [Release 9.2 to 11.2]Information in this document applies to any platform.GOALThis article deals with monitoring and tuning ...

【转载地址】http://space.itpub.net/4227/viewspace-720183首先要检查操作系统上，异步io的相关包是否已经安装，如果没有的话，通过rpm进行安装，并检查系统上异步io的参数设置：[oracle@localhost ~]$ rpm...

一般说来,异步I/O是和同步I/O相比较来说的,如果是同步I/O,当一个I/O操作执行时,应用程序必须等待,直到此I/O执行完. 相反,异步I/O操作在后台运行,I/O操作和应用程序可以同时运行,提高了系统性能; 使...