Percona XtraBackup 8.0.23 enables the lock-ddl option by default to ensure any DDL events do not corrupt the backups. Any DML events continue to occur, and only DDL events are blocked. A DDL lock protects the definition of tables and views. With the “lock-ddl” option disabled, Percona XtraBackup allows backups while concurrent DDL events continue [&]

https://www.percona.com/blog/2021/01/27/percona-xtrabackup-8-enables-lock-ddl-by-default/