Duplicating an Active Database

1/ Create a initialization parameter (initdup.ora) for the Auxiliary instance as following:
DB_NAME=dup
DIAGNOSTIC_DEST='/u01/app/oracle'
DB_FILE_NAME_CONVERT='+DATA/orcl/datafile/','+DATA/dup/datafile/','+DATA/orcl/tempfile/','+DATA/dup/tempfile/'
LOG_FILE_NAME_CONVERT='+DATA/orcl/onlinelog/','+DATA/dup/onlinelog/','+FRA/orcl/onlinelog/','+FRA/dup/onlinelog/'
CONTROL_FILES='+DATA/dup/controlfile/current.260.777510967'
2/ Copy the password file from the target database to $ORACLE_HOME/dbs and rename it orapwdup
3/ Create the necessary oracle NET connectivity in the listener.ora and the tnsnames.ora file. Confirm the connection to both the Target and the Auxiliary instance using sqlplus. In this example we are creating the duplicate database from the Auxiliary server
4/ Start the Auxiliary instance to nomount mode
export ORACLE_SID=dup
export ORACLE_HOME=/u01/app/oracle/product/11.2.0/dbhome_1
sqlplus / as sysdba
SQL> startup nomount;
SQL> exit;
5/ Start RMAN and Connect to the Database Instances
rman
RMAN> connect target sys /oracle_4U@orcl
RMAN> connect auxiliary sys /oracle_4U@dup
RMAN> connect catalog rcatowner/oracle_4U@rcat
6/ Run the duplicate database command
RMAN> DUPLICATE TARGET DATABASE TO 'dup' FROM ACTIVE DATABASE;