In previous MySQL releases, dictionary data was partially stored in metadata files. 在以前的MySQL版本中，字典数据部分存储在元数据文件中。Issues with file-based metadata storage included expensive file scans, susceptibility to file system-related bugs, complex code for handling of replication and crash recovery failure states, and a lack of extensibility that made it difficult to add metadata for new features and relational objects.基于文件的元数据存储的问题包括昂贵的文件扫描、易受文件系统相关错误的影响、处理复制和崩溃恢复故障状态的复杂代码，以及缺乏扩展性，难以为新功能和关系对象添加元数据。
The metadata files listed below are removed from MySQL. 下面列出的元数据文件将从MySQL中删除。Unless otherwise noted, data previously stored in metadata files is now stored in data dictionary tables.除非另有说明，以前存储在元数据文件中的数据现在存储在数据字典表中。
.frm files: Table metadata files. 文件：表元数据文件。With the removal of 删除.frm files:.frm文件后：
The 64KB table definition size limit imposed by the 已删除.frm file structure is removed..frm文件结构施加的64KB表定义大小限制。
The INFORMATION_SCHEMA.TABLES VERSION column reports a hardcoded value of 10, which is the last .frm file version used in MySQL 5.7.
.par files: Partition definition files. InnoDB stopped using partition definition files in MySQL 5.7 with the introduction of native partitioning support for InnoDB tables.
.TRN files: Trigger namespace files.
.TRG files: Trigger parameter files.
.isl files: InnoDB Symbolic Link files containing the location of file-per-table tablespace files created outside of the data directory.
db.opt files: Database configuration files. These files, one per database directory, contained database default character set attributes.
ddl_log.log file: The file contained records of metadata operations generated by data definition statements such as DROP TABLE and ALTER TABLE.