Symptoms

By default MariaDB allows a 16-characters usernames. However, it is possible to increase the limit for the length of database usernames according to the following article:

How to increase the limit for the length of database username in MariaDB?

After that an attempt to migrate a domain with the database user which name consists of more than 16 characters fails with the following error:

Unable to create database user 'morethan16charactersdbusername' in subscription 'example.com': Command execution failed on the local server with non-zero exit code.

command: /usr/local/psa/bin/database --create-dbuser morethan16digitaldbusername -passwd '***hidden***' -domain example.com -any-database -type mysql -server localhost:3306 -ignore-nonexistent-options

exit code: 1

stdout: 

stderr: Unable to add database user: Database user name is invalid.

Cause

The possibility to use long database usernames is a request with id #PPM-1889 and will be implemented in the future Plesk updates.

Resolution

As a workaround, apply the fix.

1. Connect to the server using SSH .

2. Download the attached archive Checker.zip and extract it:

   # wget https://support.plesk.com/hc/en-us/article_attachments/115000725194/Checker.zip
   
   # unzip Checker.zip
   

3. Create a backup of the original Checker.php :

   # mv /usr/local/psa/admin/plib/Checker.php{,_backup}
   

4. Place the fixed file instead of the original one:

   # mv Checker.php /usr/local/psa/admin/plib/
   

5. In Plesk Migrator click [Re-sync] next to example.com

6. Match Business objects and Database data and click OK :