Crosschecks are useful because they can do the following:

■ Update outdated information about backups that disappeared from disk or tape or

became corrupted

更新备份的过期信息

■ Update the repository if you delete archived redo logs or other files with operating

system commands

如果之前使用的是操作系统命令，则更新仓库信息

Use the crosscheck feature to check the status of a backup on disk or tape. If the

backup is on disk, then CROSSCHECK checks whether the header of the file is valid. If a

backup is on tape, then the command checks that the backups exist in the media

management software catalog.

使用crosscheck特性检查磁盘和磁带的备份状态。

Backup pieces and image copies can have the status AVAILABLE, EXPIRED, or

UNAVAILABLE. You can view the status of backups by running the RMAN LIST

command or by querying V$BACKUP_FILES or recovery catalog views such as RC_

DATAFILE_COPY or RC_ARCHIVED_LOG. A crosscheck updates the RMAN repository

so that all of these techniques provide accurate information. RMAN updates each

backup in the RMAN repository to status EXPIRED if the backup is no longer

available. If a new crosscheck determines that an expired backup is available again,

then RMAN updates its status to AVAILABLE.

可以通过list命令查看文件获取状态，也可以查看v$backup_files和rc_datafile_cope或rc_archived_log视图。

Note: The CROSSCHECK command does not delete operating

system files or remove repository records. You must use the

DELETE command for these operations.

You can issue the DELETE EXPIRED command to delete all expired backups. RMAN

removes the record for the expired file from the repository. If for some reason the file

still exists on the media, then RMAN issues warnings and lists the mismatched objects

that cannot be deleted.

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