For InnoDB tables in mysqldump an online backup that takes no locks on tables can be performed by . . . . . . . .

Solution (By Examveda Team)

This question is about taking a backup of your MySQL database without disrupting the normal operations. We want to ensure that the backup process doesn't interfere with users accessing or modifying data.

InnoDB is a storage engine used in MySQL. It handles transactions, which are essentially a series of operations that are treated as a single unit.

mysqldump is a command-line utility used for creating backups of your MySQL database. It generates a script that can be used to recreate the database later.

The options provided are arguments that can be used with mysqldump:
    -single-transaction: This option is commonly used for creating backups. It ensures that all the data changes in a single transaction are captured consistently. It takes a short-term lock during the backup process, but it's usually a minimal disruption.
    -multiple-transaction: This option is designed for taking backups of large databases. It breaks the backup process into multiple transactions, allowing users to continue accessing the database while the backup is in progress. However, it's not considered a "no-lock" backup as it still takes locks on the table during individual transactions.
    -double-transaction: This option is not a standard option for mysqldump. It's not related to backup procedures.
    -no-transaction: This option is not typically used for taking backups. It avoids using transactions during the backup, potentially leading to inconsistencies in the data if other processes are modifying the database concurrently.

The answer to the question is: None of the above options will provide a truly "no-lock" backup. While -multiple-transaction might seem like a suitable option, it doesn't guarantee a completely lock-free process.

To achieve a truly lock-free backup with InnoDB tables, you would need to use techniques like:
    Logical replication: This involves setting up a replication system where changes to the primary database are replicated to a secondary instance. You can then take a backup of the secondary instance without impacting the primary database.
    Percona XtraBackup: This tool is specifically designed for taking online backups of InnoDB tables. It works at the file system level, minimizing locks on tables.

The question might be designed to test your understanding of the different backup methods and their limitations.