Dictionary Cache (90)

最新推荐文章于 2025-12-19 15:39:34 发布

转载最新推荐文章于 2025-12-19 15:39:34 发布 · 207 阅读

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#数据库

本文介绍了Oracle数据库中数据字典的概念及其重要性。数据字典包含关于数据库结构和用户的参考信息，是Oracle执行SQL语句解析过程中频繁访问的对象。为了提高访问效率，Oracle在内存中设置了两个特殊区域——数据字典缓存（即行缓存）和库缓存来存储字典数据，所有用户进程共享这些缓存。

The data dictionary is a collection of database tables and views containing reference
information about the database, its structures, and its users. Oracle accesses the data
dictionary frequently during SQL statement parsing. This access is essential to the
continuing operation of Oracle.
The data dictionary is accessed so often by Oracle that two special locations in
memory are designated to hold dictionary data. One area is called the data dictionary
cache, also known as the row cache because it holds data as rows instead of buffers
(which hold entire blocks of data). The other area in memory to hold dictionary data is
the library cache. All Oracle user processes share these two caches for access to data
dictionary information.

字典高速缓存
1. 一组反应数据库信息的表或视图
2. 内存中有两个指派的地方来保存字典数据. 一是字典高速缓存也就是row cache
另一个地方就是library cache

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