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MySQL Server incorporates a transactional data dictionary that stores information about database objects. MySQL服务器集成了一个事务数据字典，用于存储有关数据库对象的信息。In previous MySQL releases, dictionary data was stored in metadata files, nontransactional tables, and storage engine-specific data dictionaries.在以前的MySQL版本中，字典数据存储在元数据文件、非事务表和存储引擎特定的数据字典中。
This chapter describes the main features, benefits, usage differences, and limitations of the data dictionary. 本章介绍数据字典的主要功能、优点、用法差异和局限性。For other implications of the data dictionary feature, refer to the “Data Dictionary Notes” section in the MySQL 8.0 Release Notes.<有关数据字典功能的其他含义，请参阅MySQL 8.0发行说明中的“数据字典注释”部分</p>
Benefits of the MySQL data dictionary include:MySQL数据字典的好处包括：
Simplicity of a centralized data dictionary schema that uniformly stores dictionary data. 一致性存储字典数据的集中式数据字典架构的简单性。See Section 14.1, “Data Dictionary Schema”.请参阅第14.1节，“数据字典架构”。
Removal of file-based metadata storage. 删除基于文件的元数据存储。See Section 14.2, “Removal of File-based Metadata Storage”.请参阅第14.2节，“删除基于文件的元数据存储”。
Transactional, crash-safe storage of dictionary data. 字典数据的事务性、崩溃安全存储。See Section 14.3, “Transactional Storage of Dictionary Data”.请参阅第14.3节，“字典数据的事务存储”。
Uniform and centralized caching for dictionary objects. 字典对象的一致性和集中缓存。See Section 14.4, “Dictionary Object Cache”.请参阅第14.4节，“字典对象缓存”。
A simpler and improved implementation for some 一种更简单和改进的实现，用于某些INFORMATION_SCHEMA tables. INFORMATION_SCHEMA表。See Section 14.5, “INFORMATION_SCHEMA and Data Dictionary Integration”.请参阅第14.5节，“信息架构和数据字典集成”。
Atomic DDL. 原子DDL。See Section 13.1.1, “Atomic Data Definition Statement Support”.请参阅第13.1.1节，“原子数据定义语句支持”。
A data dictionary-enabled server entails some general operational differences compared to a server that does not have a data dictionary; see Section 14.7, “Data Dictionary Usage Differences”. 与没有数据字典的服务器相比，启用数据字典的服务器会带来一些一般的操作差异；请参阅第14.7节，“数据字典使用差异”。Also, for upgrades to MySQL 8.0, the upgrade procedure differs somewhat from previous MySQL releases and requires that you verify the upgrade readiness of your installation by checking specific prerequisites. 此外，对于MySQL 8.0的升级，升级过程与以前的MySQL版本有所不同，需要通过检查特定的先决条件来验证安装的升级准备情况。For more information, see Section 2.11, “Upgrading MySQL”, particularly Section 2.11.5, “Preparing Your Installation for Upgrade”.有关更多信息，请参阅第2.11节，“升级MySQL”，特别是第2.11.5节，“为升级准备安装”。