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REDO INTERNALS AND TUNING BY REDO

原创 Linux操作系统 作者:kinglawrence 时间:2011-06-17 12:43:41 0 删除 编辑
Introduction(介绍)
        This paper is to explore internals of redo generation and then analyze the effect of excessive redo generation. We will substantiate common issues
that increases redo size and techniques to reduce it. We will also explore few techniques to detect excessive redo generation and how to find the root cause
of excessive redo generation.
        本文将探索REDO生成的本质,然后分析额外的REDO产生的影响。我们将证明增加REDO SIZE和技巧的通用问题以减少影响。我们将同样地探索一些技巧来发觉额外的REDO生
成和怎么来找到额外REDO生成的根本原因。
        This paper is NOT designed as a step by step approach, rather as a guideline. Every effort has been taken to reproduce the test results. It is
possible for the test results to differ slightly due to version/platform. differences.
 本文并非按STEP BY STEP方式书写,更像是一本指导书。我们尽最大努力来重现实验结果。这是有可能因为由于版本/平台的差异而导致测试结果略有不同。
 Redo generation is absolutely essential for recovery. This paper does not subscribe to the notion that the redo generation must be disabled. We
explore the options to reduce excessive redo without affecting the functional behavior. of application or recovery. We can also substantiate that reducing
redo improves application scalability and reduces MTTR (Mean time to recover).
 REDO生成最本质的目的是用于恢复。本文不同意REDO生成必须DISABLED的概念。我们探索的途径,以减少不影响应用程序或恢复功能行为过度重做。我们还可以证明,减
少重做提高了应用程序的可扩展性,降低MTTR(平均恢复时间)。
 
Redo generation in Oracle(ORACLE中的REDO生成)
 Oracle maintains ACID properties (Atomicity, Consistency, Isolation and Durability) of relational database theory. Oracle database’s redo logging
mechanism plays pivotal role in implementing these properties.
 ORACLE包含了关系性数据库的ACID属性(原子性、一致性、隔离性、持久性),ORACLE数据库的重做日志结构为保证这条规则起着关键作用。
 
 Combination of physical and logical change logging, physiological logging, implements few of these ACID properties:
  (a) Atomic change to a database block generates a change vector. This change vector is for a database block and physical in nature.
  (b) Multiple change vectors grouped together to create a redo record. This implements logical change.
 物理和逻辑变化记录,结合实现了这些ACID属性:
  (a) 数据块的原子改动产生一个改动向量,这个改动向量拥有数据块和物理性质。
  (b) 多个改动向量组合到一起就产生了一个重做记录,它形成一个逻辑改动

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