Creating backups with mysqldump is a common practice, but by default, it locks all tables, limiting write operations during the process. This guide will show you how to avoid locking tables while ensuring consistent backups for MySQL and MariaDB databases.

Run mysqldump Without Locking Tables

The Default Behavior of mysqldump

By default, mysqldump locks all tables during the backup process to ensure data consistency. While this is effective for maintaining a stable snapshot, it restricts the database to read-only mode, disrupting applications that require write access during the backup.

Why Are All Tables Locked?

The default table-locking behavior is necessary for MyISAM tables because they lack transactional support. InnoDB, on the other hand, supports transactions and ensures data consistency without requiring table locks.

Since MySQL 5.5.5 (released in 2010), InnoDB has been the default storage engine, and it is recommended for most use cases due to its robust transaction support.

How to Avoid Locking Tables

To avoid table locking during backups, use the --single-transaction and --skip-lock-tables flags with mysqldump. These options work as follows:

  • --single-transaction: Wraps the dump process in a transaction, ensuring data consistency for InnoDB tables.
  • --skip-lock-tables: Prevents mysqldump from applying the default table locks.

Example Commands:

Backup a Single Database Without Locking Tables:

mysqldump --single-transaction --skip-lock-tables my_database > my_database.sql

Backup Multiple Databases Without Locking Tables:

mysqldump --single-transaction --skip-lock-tables --databases my_db1 my_db2 > my_database.sql

Backup All Databases Without Locking Tables:

mysqldump --single-transaction --skip-lock-tables --all-databases > my_database.sql

Important Notes

Mixed Storage Engines:

If your database includes both InnoDB and MyISAM tables:

  • Using --single-transaction and --skip-lock-tables can leave MyISAM tables in an inconsistent state since it does not lock read/write operations for these tables.
  • For environments with mixed engines, consider using table locks or migrating MyISAM tables to InnoDB.

Compatibility:

These options are compatible with both MySQL and MariaDB, ensuring flexibility across database systems.

Conclusion

Using mysqldump with --single-transaction and --skip-lock-tables is a highly effective method to create consistent backups without disrupting write operations. This approach works seamlessly for InnoDB tables, but it’s important to review your storage engine configuration when applying this method.

By incorporating these flags, you can maintain database availability during backups, making it a practical solution for modern applications.