（ITPUB斑竹福哥讲解）

1、坏块

（1、物理坏块

（2、逻辑坏块

BLOCK物理损坏的特征：

   In a physical block corruption, which is also called a

   media corruption, the database does not recognize the

   block at all:

      1  the checksum is invalid,

      2  the block contains all zeros,

      3  the header and footer of the block do not match or

          one of the key data block data structure is

          incorrect such as the data block address (DBA).

   关键点：数据库并不识别BLOCK。

BLOCK逻辑损坏的特征：

    In a logical block corruption, the contents of the block are physically sound and pass the physical block checks;  however the block can be logically inconsistent.  Examples of logical corruption include corruption of a row piece or index entry.

2、RMAN常用的校验命令

    -- 检测/校验要备份的对象。

    Backup Validate Check Logical BackupSpec;   backup validate database;   ---这个是不会备份的

    -- 检测/校验要恢复的对象。

    Restore Restoreobject Check Logical  Validate;   

    -- 检测/校验备份集及要备份的对象。-两边都检查

    Validate Backupset/Db、Ts、Df、Ctl/Spfile、archivelog {Copy};