Oracle passwords can be from 1 to 30 characters – the first character in an Oracle password must be a letter – subsequent characters may be letters, numbers, or the symbols # (pound sign), $ (dollar sign) or _ (underscore)
If the Oracle password is not enclosed in quotes then it can include any letter, any digit, “_”, “#” or “$” characters. If on the other Hand you enclose the password in quotes then you can use any character in any position
Oracle passwords are not case sensitive so the valid alphabet is reduced by 26 characters