MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6

14.6.4 InnoDB Data Dictionary

The InnoDB data dictionary is comprised of internal system tables that contain metadata used to keep track of objects such as tables, indexes, and table columns. The metadata is physically located in the InnoDB system tablespace. For historical reasons, data dictionary metadata overlaps to some degree with information stored in InnoDB table metadata files (.frm files).