打算寫一系列的文章介紹11g的新特性和變化。

Oracle11g在備份和恢復方面新增了很多的功能，無論是效能、功能性、安全性和可操作性方面都有了不同程度的提高。

這一篇介紹RMAN對於UNDO表空間的最佳化。

Oracle11新特性——備份恢復功能增強（一）：http://yangtingkun.itpub.net/post/468/412991

Oracle11新特性——備份恢復功能增強（二）：http://yangtingkun.itpub.net/post/468/414647

Oracle11g新增了對於UNDO表空間的最佳化功能，對於UNDO表空間中的內容，對於恢復沒有幫助的資料，Oracle不會備份。也就是說，Oracle不備份已經提交的資料。

首先對比一下10g和11g的情況：

$ sqlplus "/ as sysdba"

SQL*Plus: Release 10.2.0.3.0 - Production on 星期六 9月 22 23:36:04 2007

連線到:
Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production
With the Partitioning, Real Application Clusters, OLAP and Data Mining options

SQL> select
2 (select sum(bytes)/1024/1024 from dba_data_files where tablespace_name = 'UNDOTBS1') total,
3 (select sum(bytes)/1024/1024 from dba_free_space where tablespace_name = 'UNDOTBS1') free
4 from dual;

TOTAL FREE
---------- ----------
2048 1960.3125

SQL> exit從 Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production
With the Partitioning, Real Application Clusters, OLAP and Data Mining options 斷開
$ rman target /

恢復管理器: Release 10.2.0.3.0 - Production on 星期六 9月 22 23:39:11 2007

連線到目標資料庫: TESTRAC (DBID=4291216984)

RMAN> run
2> {
3> allocate channel c1 device type disk format '/data1/backup/%U';
4> backup tablespace undotbs1;
5> }

使用目標資料庫控制檔案替代恢復目錄分配的通道: c1通道 c1: sid=301 例項=testrac1 devtype=DISK

啟動 backup 於 22-9月 -07通道 c1: 啟動全部資料檔案備份集通道 c1: 正在指定備份集中的資料檔案輸入資料檔案 fno=00002 name=+DISK/testrac/datafile/undotbs1.263.618591197通道 c1: 正在啟動段 1 於 22-9月 -07通道 c1: 已完成段 1 於 22-9月 -07段控制程式碼=/data1/backup/07isk6i2_1_1 標記=TAG20070922T233945 註釋=NONE通道 c1: 備份集已完成, 經過時間:00:00:03完成 backup 於 22-9月 -07

啟動 Control File and SPFILE Autobackup 於 22-9月 -07段 handle=/data/oracle/product/10.2/database/dbs/c-4291216984-20070922-00 comment=NONE完成 Control File and SPFILE Autobackup 於 22-9月 -07釋放的通道: c1

RMAN> list backup of tablespace undotbs1;

備份集列表
===================

BS 關鍵字型別 LV 大小裝置型別經過時間完成時間
------- ---- -- ---------- ----------- ------------ ----------
829 Full 88.10M DISK 00:00:03 22-9月 -07
BP 關鍵字: 1039 狀態: AVAILABLE 已壓縮: NO 標記: TAG20070922T233945段名:/data1/backup/07isk6i2_1_1
備份集 829 中的資料檔案列表
檔案 LV 型別 Ckp SCN Ckp 時間名稱
---- -- ---- ---------- ---------- ----
2 Full 5705040412 22-9月 -07 +DISK/testrac/datafile/undotbs1.263.618591197

從上面的測試看，UNDO表空間佔有了80多M的空間，而備份的大小也是80多M。

再來看看11g的情況：

[oracle@yangtk ~]$ sqlplus yangtk/yangtk

SQL*Plus: Release 11.1.0.6.0 - Production on Sat Oct 27 23:31:58 2007

Connected to:
Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> select
2 (select sum(bytes)/1024/1024 from dba_data_files where tablespace_name = 'UNDOTBS1') total,
3 (select sum(bytes)/1024/1024 from dba_free_space where tablespace_name = 'UNDOTBS1') free
4 from dual;

TOTAL FREE
---------- ----------
400 279.75

SQL> host
[oracle@yangtk ~]$ rman target /

Recovery Manager: Release 11.1.0.6.0 - Production on Sat Oct 27 23:33:26 2007

connected to target database: ORA11G (DBID=4026820313)

RMAN> backup tablespace undotbs1;

Starting backup at 27-OCT-07
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=135 device type=DISK
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00003 name=/data/oracle/oradata/ora11g/ORA11G/datafile/o1_mf_undotbs1_3d379k48_.dbf
channel ORA_DISK_1: starting piece 1 at 27-OCT-07
channel ORA_DISK_1: finished piece 1 at 27-OCT-07
piece handle=/data1/backup/0hivj3mf_1_1 tag=TAG20071027T233335 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:16
Finished backup at 27-OCT-07

RMAN> list backup of tablespace undotbs1;

List of Backup Sets
===================

BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
16 Full 432.00K DISK 00:00:18 27-OCT-07
BP Key: 16 Status: AVAILABLE Compressed: NO Tag: TAG20071027T233335
Piece Name: /data1/backup/0hivj3mf_1_1
List of Datafiles in backup set 16
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
3 Full 4148196 27-OCT-07 /data/oracle/oradata/ora11g/ORA11G/datafile/o1_mf_undotbs1_3d379k48_.dbf

11g中，UNDO表空間佔有了120M左右，但是備份的結果只有432K。

下面繼續測試：

RMAN> exit

Recovery Manager complete.
[oracle@yangtk ~]$ exit
exit

SQL> CREATE TABLE T_BACKUP AS SELECT * FROM DBA_OBJECTS WHERE 1 = 2;

Table created.

SQL> INSERT INTO T_BACKUP SELECT * FROM DBA_OBJECTS;

68467 rows created.

SQL> INSERT INTO T_BACKUP SELECT * FROM T_BACKUP;

68467 rows created.

SQL> INSERT INTO T_BACKUP SELECT * FROM T_BACKUP;

136934 rows created.

SQL> INSERT INTO T_BACKUP SELECT * FROM T_BACKUP;

273868 rows created.

SQL> UPDATE T_BACKUP SET OWNER = OWNER;

547736 rows updated.

SQL> SELECT
2 (SELECT SUM(BYTES)/1024/1024 FROM DBA_DATA_FILES WHERE TABLESPACE_NAME = 'UNDOTBS1') TOTAL,
3 (SELECT SUM(BYTES)/1024/1024 FROM DBA_FREE_SPACE WHERE TABLESPACE_NAME = 'UNDOTBS1') FREE
4 FROM DUAL;

TOTAL FREE
---------- ----------
400 251.75

SQL> HOST
[oracle@yangtk ~]$ rman target /

Recovery Manager: Release 11.1.0.6.0 - Production on Sun Oct 28 00:06:19 2007

connected to target database: ORA11G (DBID=4026820313)

RMAN> backup tablespace undotbs1;

Starting backup at 28-OCT-07
using channel ORA_DISK_1
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00003 name=/data/oracle/oradata/ora11g/ORA11G/datafile/o1_mf_undotbs1_3d379k48_.dbf
channel ORA_DISK_1: starting piece 1 at 28-OCT-07
channel ORA_DISK_1: finished piece 1 at 28-OCT-07
piece handle=/data1/backup/0iivj5l1_1_1 tag=TAG20071028T000656 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:37
Finished backup at 28-OCT-07

RMAN> list backup of tablespace undotbs1;

List of Backup Sets
===================

BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
16 Full 432.00K DISK 00:00:18 27-OCT-07
BP Key: 16 Status: AVAILABLE Compressed: NO Tag: TAG20071027T233335
Piece Name: /data1/backup/0hivj3mf_1_1
List of Datafiles in backup set 16
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
3 Full 4148196 27-OCT-07 /data/oracle/oradata/ora11g/ORA11G/datafile/o1_mf_undotbs1_3d379k48_.dbf

BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
17 Full 28.05M DISK 00:00:40 28-OCT-07
BP Key: 17 Status: AVAILABLE Compressed: NO Tag: TAG20071028T000656
Piece Name: /data1/backup/0iivj5l1_1_1
List of Datafiles in backup set 17
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
3 Full 4165861 28-OCT-07 /data/oracle/oradata/ora11g/ORA11G/datafile/o1_mf_undotbs1_3d379k48_.dbf

Oracle會備份UNDO表空間中沒有COMMIT的資料。如果將資料COMMIT後，會發現結果集又恢復了原來的大小：

RMAN> exit

Recovery Manager complete.
[oracle@yangtk ~]$ exit
exit

SQL> COMMIT;

Commit complete.

SQL> SELECT
2 (SELECT SUM(BYTES)/1024/1024 FROM DBA_DATA_FILES WHERE TABLESPACE_NAME = 'UNDOTBS1') TOTAL,
3 (SELECT SUM(BYTES)/1024/1024 FROM DBA_FREE_SPACE WHERE TABLESPACE_NAME = 'UNDOTBS1') FREE
4 FROM DUAL;

TOTAL FREE
---------- ----------
400 251.75

SQL> EXIT
Disconnected from Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
[oracle@yangtk ~]$ rman target /

Recovery Manager: Release 11.1.0.6.0 - Production on Sun Oct 28 00:12:25 2007

connected to target database: ORA11G (DBID=4026820313)

RMAN> backup tablespace undotbs1;

Starting backup at 28-OCT-07
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=170 device type=DISK
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00003 name=/data/oracle/oradata/ora11g/ORA11G/datafile/o1_mf_undotbs1_3d379k48_.dbf
channel ORA_DISK_1: starting piece 1 at 28-OCT-07
channel ORA_DISK_1: finished piece 1 at 28-OCT-07
piece handle=/data1/backup/0jivj5vk_1_1 tag=TAG20071028T001236 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:15
Finished backup at 28-OCT-07

RMAN> list backup of tablespace undotbs1;

List of Backup Sets
===================

BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
16 Full 432.00K DISK 00:00:18 27-OCT-07
BP Key: 16 Status: AVAILABLE Compressed: NO Tag: TAG20071027T233335
Piece Name: /data1/backup/0hivj3mf_1_1
List of Datafiles in backup set 16
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
3 Full 4148196 27-OCT-07 /data/oracle/oradata/ora11g/ORA11G/datafile/o1_mf_undotbs1_3d379k48_.dbf

BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
17 Full 28.05M DISK 00:00:40 28-OCT-07
BP Key: 17 Status: AVAILABLE Compressed: NO Tag: TAG20071028T000656
Piece Name: /data1/backup/0iivj5l1_1_1
List of Datafiles in backup set 17
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
3 Full 4165861 28-OCT-07 /data/oracle/oradata/ora11g/ORA11G/datafile/o1_mf_undotbs1_3d379k48_.dbf

BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
18 Full 28.08M DISK 00:00:19 28-OCT-07
BP Key: 18 Status: AVAILABLE Compressed: NO Tag: TAG20071028T001236
Piece Name: /data1/backup/0jivj5vk_1_1
List of Datafiles in backup set 18
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
3 Full 4166069 28-OCT-07 /data/oracle/oradata/ora11g/ORA11G/datafile/o1_mf_undotbs1_3d379k48_.dbf

RMAN> backup tablespace undotbs1;

Starting backup at 28-OCT-07
using channel ORA_DISK_1
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00003 name=/data/oracle/oradata/ora11g/ORA11G/datafile/o1_mf_undotbs1_3d379k48_.dbf
channel ORA_DISK_1: starting piece 1 at 28-OCT-07
channel ORA_DISK_1: finished piece 1 at 28-OCT-07
piece handle=/data1/backup/0kivj7b8_1_1 tag=TAG20071028T003551 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:15
Finished backup at 28-OCT-07

RMAN> list backup of tablespace undotbs1;

List of Backup Sets
===================

BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
16 Full 432.00K DISK 00:00:18 27-OCT-07
BP Key: 16 Status: AVAILABLE Compressed: NO Tag: TAG20071027T233335
Piece Name: /data1/backup/0hivj3mf_1_1
List of Datafiles in backup set 16
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
3 Full 4148196 27-OCT-07 /data/oracle/oradata/ora11g/ORA11G/datafile/o1_mf_undotbs1_3d379k48_.dbf

BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
17 Full 28.05M DISK 00:00:40 28-OCT-07
BP Key: 17 Status: AVAILABLE Compressed: NO Tag: TAG20071028T000656
Piece Name: /data1/backup/0iivj5l1_1_1
List of Datafiles in backup set 17
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
3 Full 4165861 28-OCT-07 /data/oracle/oradata/ora11g/ORA11G/datafile/o1_mf_undotbs1_3d379k48_.dbf

BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
18 Full 28.08M DISK 00:00:19 28-OCT-07
BP Key: 18 Status: AVAILABLE Compressed: NO Tag: TAG20071028T001236
Piece Name: /data1/backup/0jivj5vk_1_1
List of Datafiles in backup set 18
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
3 Full 4166069 28-OCT-07 /data/oracle/oradata/ora11g/ORA11G/datafile/o1_mf_undotbs1_3d379k48_.dbf

BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
19 Full 424.00K DISK 00:00:16 28-OCT-07
BP Key: 19 Status: AVAILABLE Compressed: NO Tag: TAG20071028T003551
Piece Name: /data1/backup/0kivj7b8_1_1
List of Datafiles in backup set 19
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
3 Full 4166605 28-OCT-07 /data/oracle/oradata/ora11g/ORA11G/datafile/o1_mf_undotbs1_3d379k48_.dbf

最後兩個備份都發生在COMMIT之後，唯一的區別在於一個是COMMIT剛剛結束，而第二個備份是過了一段時間才執行。

對於剛剛提交的內容，Oracle在備份的時候還無法確定是否被恢復所需要，只要過一段時間，UNDO備份的最佳化就生效了。

Oracle11新特性——備份恢復功能增強（三）

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