the password may be case sensitive
but I don't understand exacty. Do you mean you created a user and it's name SYSTEM. it's impossiple. SYSTEM user comes with installation, and usernames must be unique in database
and also if you want to set the same pasword in 11g for a user for some reasons such as password life time etc, you should use this method
select 'alter user '||username||' identified by values '||REGEXP_SUBSTR(DBMS_METADATA.get_ddl ('USER',USERNAME), '''[^'']+''')||';' from dba_users
I had created a user in sql developer, now when I am trying to connect to that user - I am getting ' ORA-01017:Invalid username/password;logon denied'.
That exception means you have provided the wrong username or password. You don't need to change the password you just need to provide the correct one.
I tried to change the password using 'alter user username identified by new_password;' command from SYS account.
That command would have worked to change the password for ANY user in the DB if you were connected as SYSDBA.
Post the results of executing that command. You need to SHOW us what you do, not just tell us.