Migrate from 32 bit to 64 bit using RMAN

I have Checked it on 10g and confirmed it is working. You can use it from 9i to 11g.

Step 1 – Take a Backup on Source 32 Bit Server:
Create a full backup of the database including all archivelogs:
RMAN> run {
allocate channel c1 type disk;
allocate channel c2 type disk;
backup database plus archivelog;
backup current controlfile; }
Step 2 : Preparing target 64 bit server:
Install the OS and Oracle Software.
Step 3 : Copy RMAN backup files from Source Server:
Use simple copy command to copy the rman backup files from source server to target server.
Step 4 : Create the pfile or copy the pfile from source server:
Create the pfile or copy the pfile from source server.
Step 5 : Bring up the database
Startup nomount the new instance.
Connect to rman and set the dbid:
$ rman target / nocatalog RMAN> set dbid=;
Restore the controlfile:
RMAN> restore controlfile from /u01/backup_32bit/;
RMAN> alter database mount;
RMAN> restore database;
Identify the archivelog till you want to do the recovery and check if you have all the backups you need to do it and run:
RMAN> run {
set until sequence xxxx;
recover database;
}
RMAN> exit
Step 6 : Migrate to 64Bit:
SQL> recover database until cancel using backup controlfile;
cancel
SQL> alter database open resetlogs migrate;
SQL> @$ORACLE_HOME/rdbms/admin/utlirp.sql
SQL> @$ORACLE_HOME/rdbms/admin/utlrp.sql
SQL> shutdown immediate;
SQL> startup