frm file
The file containing the metadata, such as the table definition, of a MariaDB table.
For backups, you must always keep the full set of .frm files along with the backup data, to be able to restore tables that are altered or dropped after the backup. Files with this extension are always included in backups produced by the mysqlbackup command of the MySQL Enterprise Backup product. If you use the ibbackup command instead, you must copy the .frm files yourself.
Although each InnoDB table has a .frm file, InnoDB maintains its own table metadata in the system tablespace; the .frm files are not needed for InnoDB to operate on InnoDB tables.
These files are backed up by the MySQL Enterprise Backup product. These files must not be modified by an ALTER TABLE operation while the backup is taking place, which is why backups that include non-InnoDB tables perform a FLUSH TABLES WITH READ LOCK operation to freeze such activity while backing up the .frm files. Restoring a backup can result in .frm files being created, changed, or removed to match the state of the database at the time of the backup.
See also ibbackup command.
See also MySQL Enterprise Backup.
See also mysqlbackup command.
See also system tablespace.