Changer MySQL RDS Parameter Groups

Your issue stems from trying to modify a parameter in a parameter group that is associated with one or more running MySQL RDS instances. To resolve this, you'll need to create a new parameter group and modify the parameter there. After that, you can associate the new parameter group with the RDS instances. Please note that a reboot is required for the changes to take effect.

Here's a step-by-step guide:

1. Create a new parameter group:

   Go to the RDS dashboard in AWS Console and click on "Parameter groups" in the navigation pane on the left. Then, click on the "Create parameter group" button. Make sure to select the same parameter group family you're using (for MySQL 8.0, it would be mysql8.0).

2. Modify the lower_case_table_names parameter in the new parameter group:

   Select your newly created parameter group and click on "Edit parameters". Find the lower_case_table_names parameter, change its value to 1, then click "Save changes".

3. Assign the new parameter group to your RDS instance:

   Go to "Databases" in the RDS dashboard and select your MySQL instance. Click on "Modify". In the "Database options" section, you'll find "DB parameter group". Select your new parameter group from the dropdown menu here. Click on "Continue" and "Modify DB Instance" at the end.

4. Reboot your RDS instance:

   You'll need to reboot your RDS instance for the new parameter value to take effect. Navigate back to "Databases", select your instance, and click on "Actions", then "Reboot".

Please note that setting lower_case_table_names to 1 on MySQL causes the server to convert all table names to lowercase on storage and lookup. This can cause issues with table names created with different lettercase, so use this setting carefully. In addition, changing this parameter on a running MySQL instance with existing tables can cause serious problems. Ideally, you should set this parameter when the MySQL instance is first initialized.

The parameter lower_case_table_names can only be set when creating a new database, you cannot change it once the database was created.

https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/MySQL.KnownIssuesAndLimitations.html#MySQL.Concepts.ParameterNotes