Certain usernames are reserved and you cannot use them for the administrator username.

• administrator
• ociadmin
• ocidbm
• ocirest
• ocirpl
• oracle-cloud-agent
• mysql.sys
• mysql.session
• mysql.infoschema
• mysql_option_tracker_persister
• mysql_rest_service_admin
• mysql_rest_service_data_provider
• mysql_rest_service_dev
• mysql_rest_service_meta_provider
• mysql_rest_service_schema_admin
• mysql_rest_service_user
• mysql_task_admin
• mysql_task_user
• rrhhuser