[20151117]关于增量备份.txt

SCOTT@book> @ &r/ver1

PORT_STRING                    VERSION        BANNER
------------------------------ -------------- --------------------------------------------------------------------------------
x86_64/Linux 2.4.xx            11.2.0.4.0     Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

RMAN> backup incremental level 0 datafile 5  format '/home/oracle/backup/inc0_example_%u.dbf' TAG='INC0';
Starting backup at 2015-11-17 10:47:42
using channel ORA_DISK_1
channel ORA_DISK_1: starting incremental level 0 datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00005 name=/mnt/ramdisk/book/example01.dbf
channel ORA_DISK_1: starting piece 1 at 2015-11-17 10:47:42
channel ORA_DISK_1: finished piece 1 at 2015-11-17 10:47:43
piece handle=/home/oracle/backup/inc0_example_40qmfume.dbf tag=INC0 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
Finished backup at 2015-11-17 10:47:43

--如果我改名删除这个增量备份呢？
$ mv inc0_example_40qmfume.dbf inc0_example_40qmfume.dbf_ORG

RMAN> backup incremental level 1 datafile 5  format '/home/oracle/backup/inc1_example_%u.dbf' TAG='INC1';

Starting backup at 2015-11-17 10:52:01
using channel ORA_DISK_1
channel ORA_DISK_1: starting incremental level 1 datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00005 name=/mnt/ramdisk/book/example01.dbf
channel ORA_DISK_1: starting piece 1 at 2015-11-17 10:52:01
channel ORA_DISK_1: finished piece 1 at 2015-11-17 10:52:02
piece handle=/home/oracle/backup/inc1_example_43qmfuuh.dbf tag=INC1 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
Finished backup at 2015-11-17 10:52:02

--增量1级备份成功。

RMAN> list backupset ;
List of Backup Sets
===================
BS Key  Type LV Size       Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ -------------------
120     Incr 0  68.84M     DISK        00:00:00     2015-11-17 10:47:42
        BP Key: 120   Status: AVAILABLE  Compressed: NO  Tag: INC0
        Piece Name: /home/oracle/backup/inc0_example_40qmfume.dbf
  List of Datafiles in backup set 120
  File LV Type Ckp SCN    Ckp Time            Name
  ---- -- ---- ---------- ------------------- ----
  5    0  Incr 1774661    2015-11-16 16:16:33 /mnt/ramdisk/book/example01.dbf

BS Key  Type LV Size       Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ -------------------
122     Incr 1  32.00K     DISK        00:00:00     2015-11-17 10:52:01
        BP Key: 122   Status: AVAILABLE  Compressed: NO  Tag: INC1
        Piece Name: /home/oracle/backup/inc1_example_43qmfuuh.dbf
  List of Datafiles in backup set 122
  File LV Type Ckp SCN    Ckp Time            Name
  ---- -- ---- ---------- ------------------- ----
  5    1  Incr 1812018    2015-11-17 10:52:01 /mnt/ramdisk/book/example01.dbf

--说明备份并不是读取增量备份文件来比较的。而是通过控制文件记录的信息来确定从那个scn开始。

SELECT recid
      ,file#
      ,incremental_level
      ,incremental_change#
      ,checkpoint_change#
      ,datafile_blocks
      ,blocks_read
  FROM V$BACKUP_DATAFILE;

     RECID      FILE# INCREMENTAL_LEVEL INCREMENTAL_CHANGE# CHECKPOINT_CHANGE# DATAFILE_BLOCKS BLOCKS_READ
---------- ---------- ----------------- ------------------- ------------------ --------------- -----------
       124          5                 0                   0            1774661           42240       39872
       126          5                 1             1774661            1812018           42240       42240

--可以从BLOCKS_READ看出，0级备份仅仅读取使用的块，而1级备份读取全部的数据块。要想充分使用增量备份最好打开块跟踪。

3.打开块跟踪文件：

SCOTT@book> alter database enable block change tracking using file '/home/oracle/backup/change_tracking.dbf';
Database altered.

RMAN> backup incremental level 1 datafile 5  format '/home/oracle/backup/inc1_example_%u.dbf' TAG='INC1';
Starting backup at 2015-11-17 11:05:02
using channel ORA_DISK_1
channel ORA_DISK_1: starting incremental level 1 datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00005 name=/mnt/ramdisk/book/example01.dbf
channel ORA_DISK_1: starting piece 1 at 2015-11-17 11:05:02
channel ORA_DISK_1: finished piece 1 at 2015-11-17 11:05:03
piece handle=/home/oracle/backup/inc1_example_44qmfvmu.dbf tag=INC1 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
Finished backup at 2015-11-17 11:05:03

SELECT recid
      ,file#
      ,incremental_level
      ,incremental_change#
      ,checkpoint_change#
      ,datafile_blocks
      ,blocks_read
  FROM V$BACKUP_DATAFILE

     RECID      FILE# INCREMENTAL_LEVEL INCREMENTAL_CHANGE# CHECKPOINT_CHANGE# DATAFILE_BLOCKS BLOCKS_READ
---------- ---------- ----------------- ------------------- ------------------ --------------- -----------
       124          5                 0                   0            1774661           42240       39872
       126          5                 1             1774661            1812018           42240       42240
       127          5                 1             1812018            1812564           42240       42240
--再只执行1次增量备份就可以看出效果了。

RMAN> backup incremental level 1 datafile 5  format '/home/oracle/backup/inc1_example_%u.dbf' TAG='INC1';

Starting backup at 2015-11-17 11:06:04
using channel ORA_DISK_1
channel ORA_DISK_1: starting incremental level 1 datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00005 name=/mnt/ramdisk/book/example01.dbf
channel ORA_DISK_1: starting piece 1 at 2015-11-17 11:06:05
channel ORA_DISK_1: finished piece 1 at 2015-11-17 11:06:06
piece handle=/home/oracle/backup/inc1_example_45qmfvot.dbf tag=INC1 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
Finished backup at 2015-11-17 11:06:06

RMAN>

SCOTT@book> /
     RECID      FILE# INCREMENTAL_LEVEL INCREMENTAL_CHANGE# CHECKPOINT_CHANGE# DATAFILE_BLOCKS BLOCKS_READ
---------- ---------- ----------------- ------------------- ------------------ --------------- -----------
       124          5                 0                   0            1774661           42240       39872
       126          5                 1             1774661            1812018           42240       42240
       127          5                 1             1812018            1812564           42240       42240
       128          5                 1             1812564            1812604           42240           1

--最后一次读取量明显减少，这样可以加快1级备份的速度。

SCOTT@book> alter database disable block change tracking ;
Database altered.

$ ll /home/oracle/backup/change_tracking.dbf
ls: /home/oracle/backup/change_tracking.dbf: No such file or directory

总结：
1.使用增量备份模式，最好打开块跟踪模式。加快1级备份以及累积备份的速度。
2.注意检查0级备份是否完好，如果删除或者损坏，后果比较严重。