Installing Oracle 11gR2 on Oracle Linux 6 - error possibly related to database (unique) name
you must edit bash-profile then install oracle database .
in that you can set oracle_home and oracle_sid and etc .
i have similar mistake and resolve it with edit bash-profile in oracle user to real and correct values 
at the end , you can refer to this article , it is useful

http://www.oracle-base.com/articles/11g/oracle-db-11gr2-installation-on-oracle-linux-6.php