ORA-00911 invalid character (Database Configuration Assistant)

I had an error as written at title while creating a database from Database Configuration Asisstant at last step when it is being created.

I tried changing the Database Name and SID and data file name that i created for my database.

My database name was DBHAMDI and i changed it to HAMDI

My database's data folder's name which i created under my ORACLE_HOME was 'data_DBHAMDI'

and i used lower case to guarentee it. 

I did not get why i had this error because there was not any wrong definition like using Non-English Character or something like this but googling showed me some sort of way like i did and It worked.

No more error :)