今天有个客户询问，为什么list backup of database显示不了所有的备份，涉及到一个参数control_file_record_keep_time
查看默认参数
SQL> show parameter control
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
control_file_record_keep_time integer 7
以下是mos上的解释
CONTROL_FILE_RECORD_KEEP_TIME specifies the minimum number of days
before a reusable record in the control file can be reused. In the event a new record needs to be added to a reusable section and the oldest record has not aged enough, the record section expands. If this parameter is set to 0, then reusable sections never expand, and records are reused as needed
Note:
This parameter applies only to records in the control file that are circularly reusable (such as archive log records and various backup records). It does not apply to records such as datafile, tablespace, and redo thread records, which are never reused unless the corresponding object is dropped from the tablespace.
control_file_record_keep_time表示控制文件里可重复使用的记录所能保存的最小天数，基于nocatalog的备份管理方式，控制文件的大小不能无限增大，所以在控制文件中只能保留一段时间的备份与恢复信息。
$contofile_record_section，可以查这个视图查询文件类型记录。
所以如果CONTROL_FILE_RECORD_KEEP_TIME的值较保留策略小，那么就会在RMAN没有废弃（obsolete）这些备份之前重写这些备份的元数据信息。因此，CONTROL_FILE_RECORD_KEEP_TIME建议设置一个大于保留策略的值。
注意：关于保留策略
CONFIGURE RETENTION POLICY TO REDUNDANCY，只能控制数据文件的保留策略，对归档日志和控制文件的备份不生效。
附录：
rman，list命令方便查阅
列出详细备份信息：备份集（Backup Sets）,镜像备份(image copies),proxy copies的信息。
RMAN> list backup;
列出信息备份信息：备份集（Backup Sets）,proxy copies信息。
RMAN> list backupset;
列出所有数据文件的备份信息
RMAN> list backup of database;
列出特定表空间的所有数据文件备份集
RMAN> list backup of tablespace users;
列出指定文件的备份信息
RMAN> list backup of datafile 1;
或
RMAN> list backup of datafile '/u01/app/oracle/oradata/epps/system01.dbf';
按备份类型列出备份
RMAN> list backup by file;
列出备份的映像副本信息
RMAN> list copy;
列出过期备份信息（backup sets, proxy copies, and image copies）。
RMAN> list expired backup;
列出过期备份信息（backup sets, proxy copies）
RMAN> list expired backupset;
按备份类型列出过期备份信息
RMAN> list expired backup by file;
列出可用的备份
RMAN> list backup summary;
列出过期的备份
RMAN> list expired backup summary;
列出某个备份集的信息
RMAN> list backupset 59139;
列出数据文件映像副本
RMAN> list copy of datafile '/u01/app/oracle/oradata/epps/system01.dbf';
列出控制文件的备份信息
RMAN> list backup of controlfile;
列出备份集中TAGE的备份片信息
RMAN> list backupset tage 'TAG20160811T000724'
列出所有备份的控制文件信息
RMAN> list backup of controlfile;
列出备份的spfile文件信息
RMAN> list backup of spfile;
查看已备份的归档日志信息
RMAN> list backup of archivelog all;
RMAN> list backup of archivelog from scn xx;
RMAN> list backup of archivelog until scn xx;
RMAN> list backup of archivelog from scn xx until scn xx;
RMAN> list backup of archivelog from logseq xx;
RMAN> list backup of archivelog until logseq xx;
RMAN> list backup of archivelog from logseq xx until logseq xx;
列出所有的归档日志
RMAN> list archivelog all;
列出所有失效的归档日志
RMAN>list expired archivelog all;
列出指定表空间的备份信息
RMAN> list copy of tablespace 'SYSTEM';