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MySQL 8.4 Reference Manual  /  MySQL Data Dictionary

Chapter 16 MySQL Data Dictionary

MySQL Server incorporates a transactional data dictionary that stores information about database objects. In previous MySQL releases, dictionary data was stored in metadata files, nontransactional tables, and storage engine-specific data dictionaries.

This chapter describes the main features, benefits, usage differences, and limitations of the data dictionary. For other implications of the data dictionary feature, refer to the“Data Dictionary Notes” section in theMySQL 8.4 Release Notes.

Benefits of the MySQL data dictionary include:

Important

A data dictionary-enabled server entails some general operational differences compared to a server that does not have a data dictionary; seeSection 16.7, “Data Dictionary Usage Differences”. 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. For more information, seeChapter 3,Upgrading MySQL, particularlySection 3.6, “Preparing Your Installation for Upgrade”.