datafile number not processed because file is read-only

Solution : http://download.oracle.com/docs/cd/B19306_01/backup.102/b14192/recov002.htm

6.2.1.1 Recovery of Databases with Read-Only Tablespaces

Read-only tablespaces may require special handling in a restore and recover operation. By default, the restore operation will skip read-only tablespaces. If a read-only tablespace is at the SCN where it became read-only after it is restored from backup, no redo will be applied to it when the rest of the database is recovered. You can force RMAN to restore any missing datafiles belonging to read-only tablespaces by using the CHECK READONLY option to the RESTORE command:

RMAN> RESTORE DATABASE CHECK READONLY;
RMAN> RECOVER DATABASE DELETE ARCHIVELOG;