I think u ment ot say db_name,
1)MAke sure no one is using the database
2)alter database backup controlfile to trace;
3)Edit this file and change database name to new one.NORESETLOGS to RESETLOGS.
4)change db_name in your init/config file
5)From svrmgrl , run this script.
In step 4:
-> Change db_name, service_name and instance_name in init.ora and/or config.ora
In step 5:
-> run script from svrmgrl @nomount to recreate the controlfile.
Open the db after recreating the controlfile, shutdown the db and restart to make sure that it opens the db cleanly.