rman作爲oracle備份與恢復工具，爲我們提供了強大的功能，其中包括對數據文件的物理和邏輯檢測以及備份文件的有效性檢測。
首先，來看一下rman對數據文件的檢測。我們知道，rman在備份數據時，會將數據讀入讀緩存，然會將數據從讀緩存寫入寫緩存並最終寫入數據庫。在從讀緩存到寫緩存的過程中，rman會進行物理一致性的檢測（db_block_checksum未true）和邏輯一致性檢測（使用了check logical選項）。例如：
SQL> show parameter db_block
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_block_buffers integer 0
db_block_checking string FALSE
db_block_checksum string TRUE
db_block_size integer 8192
SQL>
RMAN> backup tablespace test1;
Starting backup at 2014-11-06 15:12:49
using channel ORA_DISK_1
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
input datafile fno=00005 name=/home/app/oraten/oradata/oraten/test01.dbf
channel ORA_DISK_1: starting piece 1 at 2014-11-06 15:12:50
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03009: failure of backup command on ORA_DISK_1 channel at 11/06/2014 15:12:51
ORA-19566: exceeded limit of 0 corrupt blocks for file /home/app/oraten/oradata/oraten/test01.dbf
有時，我們僅僅希望驗證一下數據文件是否可以備份，而不想進行真正的備份，這是我們就可以使用validate命令了，如
RMAN> backup validate database;
Starting backup at 2014-11-06 15:14:23
using channel ORA_DISK_1
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
input datafile fno=00001 name=/home/app/oraten/oradata/oraten/system01.dbf
input datafile fno=00003 name=/home/app/oraten/oradata/oraten/sysaux01.dbf
input datafile fno=00002 name=/home/app/oraten/oradata/oraten/undotbs01.dbf
input datafile fno=00005 name=/home/app/oraten/oradata/oraten/test01.dbf
input datafile fno=00004 name=/home/app/oraten/oradata/oraten/users01.dbf
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
including current control file in backupset
including current SPFILE in backupset
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:03
Finished backup at 2014-11-06 15:14:27
下面是官方文檔中的描述：
VALIDATE Causes RMAN to scan the specified files and verify their contents, testing whether this file can be backed up. RMAN creates no output files. Use this
command periodically to check for physical and logical errors in database files.
使用validate命令可以驗證備份集的有效性，官方文檔：
To examine a backup set and report whether it can be restored. RMAN scans all of the backup pieces in the specified backup sets and looks at the checksums to verify that
the contents are intact so that the backup can be successfully restored if necessary. Use this command when you suspect that one or more backup pieces in a backup set
are missing or have been damaged. Use VALIDATE BACKUPSET to specify which backups to test; use the VALIDATE option of the RESTORE command to let RMAN
choose which backups to validate. For validating image copies, run RESTORE VALIDATE FROM DATAFILECOPY
示例：
RMAN> run {
2> set maxcorrupt for datafile 5 to 2;
3> backup database;}
RMAN> validate backupset 84;
using channel ORA_DISK_1
channel ORA_DISK_1: starting validation of datafile backupset
channel ORA_DISK_1: reading from backup piece /home/app/oraten/flash_recovery_area/ORATEN/backupset/2014_11_06/o1_mf_nnndf_TAG20141106T152820_b5p8ro7v_.bkp
channel ORA_DISK_1: restored backup piece 1
piece handle=/home/app/oraten/flash_recovery_area/ORATEN/backupset/2014_11_06/o1_mf_nnndf_TAG20141106T152820_b5p8ro7v_.bkp tag=TAG20141106T152820
channel ORA_DISK_1: validation complete, elapsed time: 00:00:01
RESTORE ... PREVIEW
該命令進行restore命令的預演，可以在任何resotre命令後加上preview來進行還原預演，這個命令只是從數據字典讀出需要的備份的元數據，不進行文件的驗證。
You can apply RESTORE ... PREVIEW to any RESTORE operation to create a detailed list of every backup to be used in the requested RESTORE operation, as well as the necessary target SCN for recovery after the RESTORE operation is complete. This command accesses the RMAN repository to query the backup metadata, but does not actually read the backup files to ensure that they can be restored.
RMAN> restore database preview;
Starting restore at 2014-11-06 15:44:28
using channel ORA_DISK_1
List of Backup Sets
===================
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ -------------------
84 Full 551.76M DISK 00:00:18 2014-11-06 15:28:24
BP Key: 52 Status: AVAILABLE Compressed: NO Tag: TAG20141106T152820
Piece Name: /home/app/oraten/flash_recovery_area/ORATEN/backupset/2014_11_06/o1_mf_nnndf_TAG20141106T152820_b5p8ro7v_.bkp
List of Datafiles in backup set 84
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- ------------------- ----
1 Full 922948 2014-11-06 15:28:20 /home/app/oraten/oradata/oraten/system01.dbf
2 Full 922948 2014-11-06 15:28:20 /home/app/oraten/oradata/oraten/undotbs01.dbf
3 Full 922948 2014-11-06 15:28:20 /home/app/oraten/oradata/oraten/sysaux01.dbf
4 Full 922948 2014-11-06 15:28:20 /home/app/oraten/oradata/oraten/users01.dbf
5 Full 922948 2014-11-06 15:28:20 /home/app/oraten/oradata/oraten/test01.dbf
archive logs generated after SCN 922948 not found in repository
Media recovery start SCN is 922948
Recovery must be done beyond SCN 922948 to clear data files fuzziness
Finished restore at 2014-11-06 15:44:28
RECOVER ... TEST：在內存中模擬recover過程，並不進行真正的recovery，可以用該命令來提起發現recovery中的問題。注意，模擬的recovery和正常recovery可能會遇到不同的問題。
A simulated recovery initiated with the RECOVER ... TEST command in RMAN or SQL*Plus. A trial recovery applies redo in a way similar to normal media recovery, but it never writes its changes to disk and it always rolls back its changes. Trial recovery occurs only in memory.
Trial recovery lets you foresee what problems might occur if you were to continue with normal recovery. For problems caused by ongoing memory corruption, trial recovery and normal recovery can encounter different errors.