rac环境，用rman全备份后，将文件拷贝到一台单机oracle上用rman恢复时报错

channel ORA_DISK_1: restoring control file

RMAN-00571: ===========================================================

RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============

RMAN-00571: ===========================================================

RMAN-03002: failure of restore command at 07/09/2013 21:14:27

ORA-19870: error reading backup piece /oracle/backup_oracle/cf_5238_1_816642228

ORA-19504: failed to create file "/oracle/app/oracle/controlfile/"

ORA-27040: file create error, unable to create file

Linux-x86_64 Error: 21: Is a directory

用rman检验过cf文件的完整性，"/oracle/app/oracle/controlfile/"这个位置文件夹也正确，权限也正常