With Plesk repair utility you can easily check and repair the Mysql Databases servers , it verifies the integrity of MySQL databases and database users. Use the following commands accordingly.
Login to your Plesk Onyx server with root user
In order to Check the availability of MySQL database servers and verify the integrity of MySQL databases and database user use the command as
plesk repair mysql
In order to Check that the MySQL database servers registered in Plesk are available and can be connected to use the command as
plesk repair mysql -connection
In order to Check that all MySQL database users created in Plesk exist on the database servers. Checks database users' privileges and corrects them in case of discrepancies. Recreates any database users that are missing with the command
plesk repair mysql -database-users