oracle联机热备份的原理

核心提示： BS KeyType LV Size Device Type Elapsed Time Completion Time--- -- -- --- ---3 Full1M DISK00:00:02 31-MAR-05BP Key: 3 Status: AVAILABLECompresse

BS Key　Type LV Size　　　 Device Type Elapsed Time Completion Time

------- ---- -- ---------- ----------- ------------ ---------------

3　　　 Full　　1M　　　　 DISK　　　　00:00:02　　 31-MAR-05

BP Key: 3　 Status: AVAILABLE　Compressed: NO　Tag: TAG20050331T153729

Piece Name: /u03/oraclebk/SALES_USERS_4.bk

List of Datafiles in backup set 3

File LV Type Ckp SCN　　Ckp Time　Name

---- -- ---- ---------- --------- ----

4　　　 Full 546792　　 31-MAR-05 /u02/oradata/sales/users01.dbf

恢复的时候应用546792开始到现在的归档日志和重做日志.

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rman的增量备份的基本原理

其实原理很简单，主要就是弄明白怎么样在做增量备份时确定某个数据块需要备份，哪个不需要

rman在做1级备份的时候怎么来确定0级备份之后都有哪些数据块做了修改呢？看下面一段

Each data block in a datafile contains a system change number (SCN), which is the

SCN at which the most recent change was made to the block. During an incremental

backup, RMAN reads the SCN of each data block in the input file and compares it to

the checkpoint SCN of the parent incremental backup. If the SCN in the input data

block is greater than or equal to the checkpoint SCN of the parent, then RMAN copies

the block.

原来block里边也有一个change scn

也就是说在做level 1级备份的时候，需要扫描所有的数据块并且用块中记录修改的SCN