4.4 Backing Up and Restoring a Single .ibd File

A table with a table-specific tablespace (stored in an .ibd file) can be restored individually without taking down the MySQL server. This technique is applicable if you delete or update the table data by mistake, without actually losing the table itself through a DROP TABLE, TRUNCATE TABLE, or DROP DATABASE statement.

If you have a clean backup of an .ibd file, you can restore it to the MySQL installation from which it originated as follows:

For MySQL 5.5 and earlier, the table must already exist and not have been dropped or truncated since taking the backup. When an InnoDB table is truncated, or dropped and recreated, it gets a new table ID. Any ID mismatch between the table in the database and the backed-up table can prevent it from being restored. The requirement for matching table IDs is also the reason why you must restore to the same MySQL server from which the backup data came, not another server with a similar set of databases and tables. This restriction does not apply to MySQL 5.6 and later, as long as the restoration is made from one Generally Available (GA) version to another in the same series of MySQL servers.
Prevent write operations for the table to be restored. This prevents users from modifying the table while the restore is in progress.
```
LOCK TABLES tbl_name WRITE;
```
Issue this ALTER TABLE statement:
```
ALTER TABLE tbl_name DISCARD TABLESPACE;
```
Caution: This deletes the current .ibd file.
Copy the backup .ibd file back to the appropriate database directory.

Issue this ALTER TABLE statement:

ALTER TABLE tbl_name IMPORT TABLESPACE;

Release the write lock to complete the restore procedure:
```
UNLOCK TABLES;
```

In this context, a clean.ibd file backup means:

There are no uncommitted modifications by transactions in the .ibd file.
There are no unmerged insert buffer entries in the .ibd file.
Purge has removed all delete-marked index records from the .ibd file.
mysqld has flushed all modified pages of the .ibd file from the buffer pool to the file.

You can make such a clean backup .ibd file with the following method:

Stop all activity from the mysqld server and commit all transactions.
Wait until SHOW INNODB STATUS shows that there are no active transactions in the database, and the main thread status of InnoDB is Waiting for server activity. Then you can make a copy of the .ibd file.

Another method for making a clean copy of an .ibd file is to use mysqlbackup:

Use mysqlbackup with the --only-innodb or --only-innodb-with-frm option to back up the InnoDB installation.
Run mysqlbackup ... apply-log to create a consistent version of the backup database.
Start a second (dummy) mysqld server on the backup and let it clean up the .ibd files in the backup. Wait for the cleanup to end.
Shut down the dummy mysqld server.
Take a clean .ibd file from the backup.