I got an error while using mysqldump

*mysqldump: Got error: 1044: Access denied for user x\@y to database z
when using LOCK TABLES*

To solve this problem, either ask you administrator to grant you the lock privileges, or use the following command instead.

mysqldump -u username -p database --single-transaction >dump.sql

This is the help entry for the keyword

              Creates a consistent snapshot by dumping all tables in a
              single transaction. Works ONLY for tables stored in
              storage engines which support multiversioning (currently
              only InnoDB does); the dump is NOT guaranteed to be
              consistent for other storage engines. While a
              --single-transaction dump is in process, to ensure a
              valid dump file (correct table contents and binary log
              position), no other connection should use the following
              statements: ALTER TABLE, DROP TABLE, RENAME TABLE,
              TRUNCATE TABLE, as consistent snapshot is not isolated
              from them. Option automatically turns off --lock-tables.