Step -1
login to sqlplus
Step-2
shutdown immediate;
Step-3
startup mount exclusive restrict;
Setp-4
drop database;
Step-5
Then exit from sqlplus
Step-6
Again log into sqlplus and enter below command
startup nomount pfile='$ORACLE_HOME/dbs/initTEST.ora';
Note: Your oracle home path
Step-7
Then exit from sqlplus and log in to RMAN using below command
rman auxiliary /
Step-8
To start databse duplication enter below command , before that copy rman backup files to the correct path and give permission to oracle.
duplicate database to 'NEWDBNAME' backup location '/backup location path /' nofilenamecheck;
Then start the rman re installation .