Multiple Database Block Sizes and the Buffer Cache

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Multiple Database Block Sizes and the Buffer Cache

In oracle 10g we can have multiple block sizes at the same time. When a tablespace is created we can assign a block size for the objects that will be created in that tablespace. The DB_BLOCK_SIZE parameter in your initialization parameter file determ…

Oracle优化 -- 关于Database Buffer Cache相关参数DB_CACHE_SIZE的优化设置

select size_for_estimate, buffers_for_estimate ,ESTD_PHYSICAL_READ_factor,ESTD_PHYSICAL_READS from v$db_cache_advice 2 where block_size='8192' and advice_status='ON'; 中,size_for_estimate表示预计的数据库高速缓冲区的大小(即:db_cache_size的值).ESTD_PHYSICAL_READS表…

BUFFER CACHE之主要的等待事件

原因:资源紧张,等待其释放. 原因的原因:1. lgwr和DBWn进程写太慢:2. Buffer和latch不可用原因的原因的原因:全表扫描.library cache latches数太多等. 视图:V$SYSTEM_EVENT (instance-level waits), V$SESSION_EVENT (session-level waits) 注意: 等待与共享池和缓冲池中的高命中率(high hit ratios)无关!换句话说,高命中率也会有长时间的等待. * Buffer Bu…

Tuning 04 Sizing the Buffer Cache

Buffer Cache 特性 The buffer cache holds copies of the data blocks from the data files. Because the buffer cache is a part of the SGA, these blocks can be shared by all users. The server processes read data from the data files into buffer cache.(是serve…

相克军_Oracle体系_随堂笔记005-Database buffer cache

本章主要阐述SGA中的Database buffer cache. Buffer cache { 1.pin (读写瞬间的状态) 2.clean 3.dirty 4.unused } --Database buffer cache 概述: 1.段.区.块的概念: create table t2 ( id int, name varchar2(30) ); 建立一个表,同时建立一个段, 建立段的同时,会给段分配一个区, 区是物理上连续的几个块. 区是oracle给段分配的最小单位.…

BUFFER CACHE之调整buffer cache的大小

Buffer Cache存放真正数据的缓冲区,shared Pool里面存放的是sql指令(LC中一次编译,多次运行,加快处理性能,cache hit ratio要高),而buffer cache里面存放真正的查询结果.Buffer Cache:由彼此独立的三个子cache(subcaches,也叫主buffer cache:keep,recycle,default)组成支持多种数据块的多缓冲池.注意system表空间只能用主数据块 Step1: 查看各个组件size(看buffer cache…