- Plesk Onyx for Windows
- Add username and underscore to the beginning of database user names is used in Plesk > Tools & Settings > Database Hosting Preferences
- Unable to create a database with username longer then 16 characters:
PLESK_ERROR: Error: Database user name is invalid. Only latin letters are allowed in the database user name
Plesk 17.0-17.8 doesn't allow to create mysql database users longer then 16 characters.
Such unclear error is a bug PPPM-10708 that will be fixed in future Plesk updates.
Create database with username less then 16 characters or upgrade Plesk to Plesk Obsidian. Plesk Obsidian using up to 32 characters in MySQL 5.7 or up to 80 characters in MariaDB 10.0 and higher versions.