===基础知识补充
RMAN> CONFIGURE RETENTION POLICY TO REDUNDANCY 3;  ---配置保留策略，冗余3份
RMAN> crosscheck backup;                                                        ---检查备份集
RMAN> delete noprompt expired backup;                                  ---删除过期备份集（磁盘或磁带上备份集被手动删除）
RMAN> crosscheck copy;                                                           ---检查备份集的copy或归档日志文件
RMAN> delete noprompt expired copy;                                      ---删除过期备份集的copy或归档日志文件
RMAN> delete noprompt obsolete;                                            ---删除过时的备份集（和保留策略相关）

===现象：RMAN删除过时备份，报错ORA-19606
RMAN> delete obsolete;
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03009: failure of delete command on ORA_DISK_1 channel at 09/02/2019 08:00:44
ORA-19606: Cannot copy or restore to snapshot control file

===解决办法：重建 snapshot controlfile文件

RMAN> configure snapshot controlfile name TO '/u01/app/oracle/product/11.2.0/dbs/snapcf_aps.f_bak';   ---重命名SNAPSHOT控制文件

RMAN> crosscheck controlfilecopy '/u01/app/oracle/product/11.2.0/dbs/snapcf_aps.f';                          ---crosscheck controlfilecopy快照控制文件

RMAN> delete expired controlfilecopy '/u01/app/oracle/product/11.2.0/dbs/snapcf_aps.f';                     ---删除过期controlfilecopy快照控制文件

RMAN> configure snapshot controlfile name to /u01/app/oracle/product/11.2.0/dbs/snapcf_aps.f';       ---重新配置快照控制文件

RMAN> configure snapshot controlfile name clear;                                                                                 ---配置默认快照控制文件

至此，就可以再执行上面的删除命令了。