Error when exporting a dump in plesk databases (See:https://docs.plesk.com/en-US/onyx/reseller-guide/website-management/website-databases/exporting-and-importing-database-dumps.69538/):

Warning: Using unique option prefix database instead of databases is deprecated and will be removed in a future release. Please use the full name instead.

Cause

key_buffer and myisam-recover are deprecated in Mysql 5.5. myisam-recover option is renamed as of MySQL 5.5.3 to myisam-recover-options .
Resolution

1. Log in to Plesk server via SSH

2. Correct /etc/my.cnf or /etc/mysql/my.cnf as below:
Change pass to password
See – https://serverfault.com/questions/670648/mysqldump-complains-about-chosen-databases-regardless-of-command-line