Just downloaded the Dino Date app for Oracle 19.3 recently and I get the "ORA-65096: invalid common user or role name" error:
[oracle@localhost coreDatabase]$ sqlplus sys@orclcdb as sysdba
SQL*Plus: Release 19.0.0.0.0 - Production on Sat Dec 5 01:16:15 2020
Version 19.3.0.0.0
Copyright (c) 1982, 2019, Oracle. All rights reserved.
Enter password:
Connected to:
Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.3.0.0.0
SQL> @dd_master_install
PL/SQL procedure successfully completed.
CREATE USER dd IDENTIFIED BY dd
*
ERROR at line 1:
ORA-65096: invalid common user or role name
Disconnected from Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.3.0.0.0
[oracle@localhost coreDatabase]$
ORA-65096: invalid common user or role name
Cause: An attempt was made to create a common user or role with a name that was not valid for common users or roles. In addition to the usual rules for user and role names, common user and role names must consist only of ASCII characters, and must contain the prefix specified in common_user_prefix parameter.
Action: Specify a valid common user or role name.