Shulou(Shulou.com)06/01 Report--

The FLUSH TABLES WITH READ LOCK statement closes all open tables and adds a global read-only lock to all database tables.

This is very convenient for backup. If you have a file system like Veritas or ZFS, you can take a snapshot of the backup.

You can also directly copy the table files to be backed up to the backup directory

Cp-r / data_dir/ / back_dir

Use the UNLOCK TABLES statement to release the lock.

-- example one

-- session ①

Mysql > FLUSH TABLES WITH READ LOCK

Query OK, 0 rows affected (0.04 sec)

-- session ②, DML operation will hang

Mysql > insert into test values.

-- session ①

Mysql > UNLOCK TABLES

Query OK, 0 rows affected (0.01 sec)

-- session ②, DML operation succeeded

Mysql > insert into test values.

Query OK, 1 row affected (18 min 44.54 sec)

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