惜分飞

rman backup 对于truncate和drop等相关操作的extent到底是怎么处理的,这里通过rman backup 结合odu证明出来,在较新版本的rman中,rman backup 并未完全的备份这些被认为不需要的extent.
创建模拟环境

SQL> select * from v$version;
 
BANNER
----------------------------------------------------------------
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - Prod
PL/SQL Release 10.2.0.4.0 - Production
CORE    10.2.0.4.0      Production
TNS for Linux: Version 10.2.0.4.0 - Production
NLSRTL Version 10.2.0.4.0 - Production

SQL> create tablespace xifenfei datafile '/u01/oracle/oradata/XFF/xifenfei01.dbf' 
   2 size 10m autoextend on maxsize 10g;

Tablespace created.

SQL> conn chf/xifenfei
Connected.

SQL> create table t_xifenfei tablespace xifenfei
  2  as
  3  select * from dba_objects;

Table created.

SQL> insert into t_xifenfei
  2  select * from dba_objects;

50055 rows created.

SQL> commit;

Commit complete.

SQL> select BYTES from dba_free_space where TABLESPACE_NAME='XIFENFEI';

     BYTES
----------
    983040

SQL> select BYTES from v$datafile where name='/u01/oracle/oradata/XFF/xifenfei01.dbf';

     BYTES
----------
  12582912

SQL> select 12582912-983040 from dual;

12582912-983040
---------------
       11599872

SQL> select object_id,data_object_id from dba_objects where object_name='T_XIFENFEI';

 OBJECT_ID DATA_OBJECT_ID
---------- --------------
     51833          51833

--这里我们得到信息有:
--1.dataobj#=51833
--2.使用数据文件空间为:11599872

rman备份no truncate table 数据文件

[oracle@xifenfei ~]$ rman target /

Recovery Manager: Release 10.2.0.4.0 - Production on Thu Dec 15 06:00:05 2011

Copyright (c) 1982, 2007, Oracle.  All rights reserved.

connected to target database: XFF (DBID=3440302261)

RMAN> backup tablespace xifenfei format '/u01/oracle/oradata/tmp/no_truncate_xifenfei';

Starting backup at 15-DEC-11
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=158 devtype=DISK
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
input datafile fno=00005 name=/u01/oracle/oradata/XFF/xifenfei01.dbf
channel ORA_DISK_1: starting piece 1 at 15-DEC-11
channel ORA_DISK_1: finished piece 1 at 15-DEC-11
piece handle=/u01/oracle/oradata/tmp/no_truncate_xifenfei tag=TAG20111215T060343 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:03
Finished backup at 15-DEC-11

truncate table 操作

[oracle@xifenfei ~]$ sqlplus / as sysdba

SQL*Plus: Release 10.2.0.4.0 - Production on Thu Dec 15 06:03:58 2011

Copyright (c) 1982, 2007, Oracle.  All Rights Reserved.


Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> truncate table chf.t_xifenfei;

Table truncated.

rman备份truncate table 数据文件

RMAN> backup tablespace xifenfei format '/u01/oracle/oradata/tmp/truncate_xifenfei';

Starting backup at 15-DEC-11
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=140 devtype=DISK
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
input datafile fno=00005 name=/u01/oracle/oradata/XFF/xifenfei01.dbf
channel ORA_DISK_1: starting piece 1 at 15-DEC-11
channel ORA_DISK_1: finished piece 1 at 15-DEC-11
piece handle=/u01/oracle/oradata/tmp/truncate_xifenfei tag=TAG20111215T060445 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
Finished backup at 15-DEC-11

[root@xifenfei ~]# ls -l /u01/oracle/oradata/tmp/*_xifenfei
-rw-r----- 1 oracle oinstall 11640832 Dec 15 06:03 /u01/oracle/oradata/tmp/no_truncate_xifenfei
-rw-r----- 1 oracle oinstall   630784 Dec 15 06:04 /u01/oracle/oradata/tmp/truncate_xifenfei

odu挖rman备份前数据文件

ODU> unload dict
CLUSTER C_USER# file_no: 1 block_no: 89
TABLE OBJ$ file_no: 1 block_no: 121
CLUSTER C_OBJ# file_no: 1 block_no: 25
CLUSTER C_OBJ# file_no: 1 block_no: 25
found IND$'s obj# 19
found IND$'s dataobj#:2,ts#:0,file#:1,block#:25,tab#:3
found TABPART$'s obj# 266
found TABPART$'s dataobj#:266,ts#:0,file#:1,block#:2121,tab#:0
found INDPART$'s obj# 271
found INDPART$'s dataobj#:271,ts#:0,file#:1,block#:2161,tab#:0
found TABSUBPART$'s obj# 278
found TABSUBPART$'s dataobj#:278,ts#:0,file#:1,block#:2217,tab#:0
found INDSUBPART$'s obj# 283
found INDSUBPART$'s dataobj#:283,ts#:0,file#:1,block#:2257,tab#:0
found IND$'s obj# 19
found IND$'s dataobj#:2,ts#:0,file#:1,block#:25,tab#:3
found LOB$'s obj# 151
found LOB$'s dataobj#:2,ts#:0,file#:1,block#:25,tab#:6
found LOBFRAG$'s obj# 299
found LOBFRAG$'s dataobj#:299,ts#:0,file#:1,block#:2393,tab#:0

ODU> scan extent tablespace 6

scan extent start: 2011-12-15 06:12:28
scanning extent...
scanning extent finished.
scan extent completed: 2011-12-15 06:12:28

ODU> unload table chf.t_xifenfei object 51833 

Unloading table: T_XIFENFEI,object ID: 51833
Unloading segment,storage(Obj#=51833 DataObj#=51833 TS#=6 File#=5 Block#=11 Cluster=0)
100110 rows unloaded
--这里可以看到odu全部找到被truncate掉的记录条数

使用rman 备份后数据文件

SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> exit
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
[oracle@xifenfei odu]$ rm /u01/oracle/oradata/XFF/xifenfei01.dbf
[oracle@xifenfei odu]$ rman target /

Recovery Manager: Release 10.2.0.4.0 - Production on Thu Dec 15 06:14:00 2011

Copyright (c) 1982, 2007, Oracle.  All rights reserved.

connected to target database (not started)

RMAN> startup mount;

Oracle instance started
database mounted

Total System Global Area     318767104 bytes

Fixed Size                     1267236 bytes
Variable Size                104860124 bytes
Database Buffers             205520896 bytes
Redo Buffers                   7118848 bytes

RMAN> restore datafile 5;

Starting restore at 15-DEC-11
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=157 devtype=DISK

channel ORA_DISK_1: starting datafile backupset restore
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
restoring datafile 00005 to /u01/oracle/oradata/XFF/xifenfei01.dbf
channel ORA_DISK_1: reading from backup piece /u01/oracle/oradata/tmp/truncate_xifenfei
channel ORA_DISK_1: restored backup piece 1
piece handle=/u01/oracle/oradata/tmp/truncate_xifenfei tag=TAG20111215T060445
channel ORA_DISK_1: restore complete, elapsed time: 00:00:01
Finished restore at 15-DEC-11

odu挖rman还原后数据文件

ODU> scan extent tablespace 6

scan extent start: 2011-12-15 06:14:43
scanning extent...
scanning extent finished.
scan extent completed: 2011-12-15 06:14:43

ODU>  unload table chf.t_xifenfei object 51833 

Unloading table: T_XIFENFEI,object ID: 51833
Unloading segment,storage(Obj#=51833 DataObj#=51833 TS#=6 File#=5 Block#=11 Cluster=0)
4774 rows unloaded
--odu只找到极少数数据4774/100110

通过odu挖rman备份前和备份后的数据文件,得知rman backup备份的过程,对绝大多数truncate的表的原始数据未正常备份(为什么是绝大多数,我无法给出解释),这里也可以看出rman backup并非是真正意义上的完全物理上复制(和rman copy还是有区别,copy不能完全被取代)

有不少人对于rman的backup功能,到底备份数据文件的什么级别,一直有着不明确的说法,我这里以10.2.0.4版本的rman backup 测试,进行一个简单的说明.这里提供的是一种思路.如果你在实际工作中,遇到一些rman到底会不会备份相关数据块的时候,可以通过类此的试验来证明你的版本的rman的功能.
模拟环境

SQL> select * from v$version;

BANNER
----------------------------------------------------------------
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - Prod
PL/SQL Release 10.2.0.4.0 - Production
CORE    10.2.0.4.0      Production
TNS for Linux: Version 10.2.0.4.0 - Production
NLSRTL Version 10.2.0.4.0 - Production

SQL> create tablespace xifenfei datafile '/u01/oracle/oradata/XFF/xifenfei01.dbf' 
   2 size 10m autoextend on next 10m maxsize 30g;

Tablespace created.

备份空数据文件

SQL> select BYTES from v$datafile where name='/u01/oracle/oradata/XFF/xifenfei01.dbf';

     BYTES
----------
  10485760

SQL> select BYTES from dba_free_space where TABLESPACE_NAME='XIFENFEI';

     BYTES
----------
  10420224

SQL> SELECT 10485760-10420224 FROM DUAL;

10485760-10420224
-----------------
            65536

RMAN> backup tablespace xifenfei format '/u01/oracle/oradata/tmp/no_table_xifenfei';

[root@xifenfei tmp]# ls -l no_table_xifenfei
-rw-r----- 1 oracle oinstall 106496 Dec 15 01:03 no_table_xifenfei

从这里可以看出来rman备份的时候,数据文件中未格式化的块并没有备份(数据文件10m,备份集只有106k左右,比文件实际使用的65536b稍微大点)

备份create表数据文件

SQL> create table t_rman tablespace xifenfei
  2  as
  3  select * from chf.t_xifenfei1;

Table created.

SQL> select BYTES from dba_free_space where TABLESPACE_NAME='XIFENFEI';

     BYTES
----------
   9371648

SQL> select BYTES from v$datafile where name='/u01/oracle/oradata/XFF/xifenfei01.dbf';

     BYTES
----------
  20971520

SQL> select 20971520-9371648 from dual;

20971520-9371648
----------------
        11599872

RMAN> backup tablespace xifenfei format '/u01/oracle/oradata/tmp/crt_table_xifenfei';

[root@xifenfei ~]# ls -l /u01/oracle/oradata/tmp/crt_table_xifenfei
-rw-r----- 1 oracle oinstall 11608064 Dec 15 01:29 /u01/oracle/oradata/tmp/crt_table_xifenfei

这里可以得出结论,rman的备份集大小可以从一定程度上近似等于数据文件使用空间大小

备份truncate表数据文件

SQL> truncate table t_rman;

Table truncated.

SQL> SELECT 20840448-9371648 from dual;

20840448-9371648
----------------
        11468800

SQL> select 20971520-20840448 from dual;

20971520-20840448
-----------------
           131072

RMAN>  backup tablespace xifenfei format '/u01/oracle/oradata/tmp/truncate_table_xifenfei';

[root@xifenfei ~]# ls -l /u01/oracle/oradata/tmp/truncate_table_xifenfei
-rw-r----- 1 oracle oinstall 630784 Dec 15 01:30 /u01/oracle/oradata/tmp/truncate_table_xifenfei

通过这里可以看出来,truncate 对象后,数据文件释放了对象空间,rman备份集也同样未备份这部分空间

备份insert表数据文件

SQL> insert into t_rman  select * from chf.t_xifenfei1;

100062 rows created.

SQL> commit;

Commit complete.

SQL> alter system checkpoint;

System altered.

SQL> select BYTES from v$datafile where name='/u01/oracle/oradata/XFF/xifenfei01.dbf';

     BYTES
----------
  20971520

SQL> select BYTES from dba_free_space where TABLESPACE_NAME='XIFENFEI';

     BYTES
----------
   9371648

SQL>  select 20971520 - 9371648 from dual;

20971520-9371648
----------------
        11599872

RMAN> backup tablespace xifenfei format '/u01/oracle/oradata/tmp/insert_table_xifenfei';

[root@xifenfei ~]# ls -l /u01/oracle/oradata/tmp/insert_table_xifenfei
-rw-r----- 1 oracle oinstall 11640832 Dec 15 02:19 /u01/oracle/oradata/tmp/insert_table_xifenfei

和直接创建表的出来结论相似

备份delete表数据文件

SQL> delete from t_rman;

100062 rows deleted.

SQL> commit;

Commit complete.

SQL>  alter system checkpoint;

System altered.

SQL> select BYTES from v$datafile where name='/u01/oracle/oradata/XFF/xifenfei01.dbf';

     BYTES
----------
  20971520

SQL>  select BYTES from dba_free_space where TABLESPACE_NAME='XIFENFEI';

     BYTES
----------
   9371648

SQL> select 20971520 - 9371648 from dual;

20971520-9371648
----------------
        11599872

RMAN> backup tablespace xifenfei format '/u01/oracle/oradata/tmp/delete_table_xifenfei';

[root@xifenfei ~]# ls -l /u01/oracle/oradata/tmp/delete_table_xifenfei
-rw-r----- 1 oracle oinstall 11640832 Dec 15 02:45 /u01/oracle/oradata/tmp/delete_table_xifenfei

这里是直接delete数据,产生了明显的高水位现象(高水位之下部分无数据),但是rman备份,还是会备份高水位之下的所有数据

备份drop表数据文件

SQL> drop table t_rman;

Table dropped.

SQL> select BYTES from v$datafile where name='/u01/oracle/oradata/XFF/xifenfei01.dbf';

     BYTES
----------
  20971520

SQL> select BYTES from v$datafile where name='/u01/oracle/oradata/XFF/xifenfei01.dbf';

     BYTES
----------
  20971520
SQL> select sum(bytes) from  dba_free_space where TABLESPACE_NAME='XIFENFEI';

SUM(BYTES)
----------
  20905984

SQL> select 20971520-20905984 from dual;

20971520-20905984
-----------------
            65536

RMAN> backup tablespace xifenfei format '/u01/oracle/oradata/tmp/drop_table_xifenfei';

[root@xifenfei ~]# ls -l /u01/oracle/oradata/tmp/drop_table_xifenfei
-rw-r----- 1 oracle oinstall 11640832 Dec 15 02:51 /u01/oracle/oradata/tmp/drop_table_xifenfei

在10g中,因为默认使用回收站功能,对象还存在回收站中,rman为了使得还原出来的数据库可以继续使用回收站中相应的表的闪回功能,所以也会备份回收站中数据

备份purge表数据文件

SQL> select OBJECT_NAME,ORIGINAL_NAME from user_recyclebin;

OBJECT_NAME                    ORIGINAL_NAME
------------------------------ --------------------------------
BIN$tBHa31bTe3jgQKjACgEImw==$0 T_RMAN

SQL> purge table "BIN$tBHa31bTe3jgQKjACgEImw==$0";

Table purged.

RMAN> backup tablespace xifenfei format '/u01/oracle/oradata/tmp/PURGE_table_xifenfei';

[root@xifenfei ~]# ls -l /u01/oracle/oradata/tmp/PURGE_table_xifenfei
-rw-r----- 1 oracle oinstall 106496 Dec 15 03:08 /u01/oracle/oradata/tmp/PURGE_table_xifenfei

可以看到purge表之后,其实效果类此truncate(当然truncate做的工作更多),rman备份集大小和无数据对象时相同,结合drop和purge也可以知道在删除大对象或者比较多对象而且又确定不再需要,且有rman备份,这个时候建议直接加上purge.

各个备份集汇总

[root@xifenfei tmp]# ll *table_xifenfei
-rw-r----- 1 oracle oinstall 11608064 Dec 15 01:29 crt_table_xifenfei
-rw-r----- 1 oracle oinstall 11640832 Dec 15 02:45 delete_table_xifenfei
-rw-r----- 1 oracle oinstall 11640832 Dec 15 02:51 drop_table_xifenfei
-rw-r----- 1 oracle oinstall 11640832 Dec 15 02:19 insert_table_xifenfei
-rw-r----- 1 oracle oinstall   106496 Dec 15 01:03 no_table_xifenfei
-rw-r----- 1 oracle oinstall   106496 Dec 15 03:08 PURGE_table_xifenfei
-rw-r----- 1 oracle oinstall   630784 Dec 15 01:30 truncate_table_xifenfei

rman的备份功能本身就是在不断的增强,不同的版本会有不同的结果,最明显的就是在9i版本会备份truncate的数据.

SQL> select * from v$version;

BANNER
----------------------------------------------------------------
Oracle9i Enterprise Edition Release 9.2.0.4.0 - Production
PL/SQL Release 9.2.0.4.0 - Production
CORE    9.2.0.3.0       Production
TNS for Linux: Version 9.2.0.4.0 - Production
NLSRTL Version 9.2.0.4.0 - Production

SQL> create tablespace xifenfei datafile
  2  '/u01/oracle/oradata/xifenfei/xifenfei01.dbf' size 10m autoextend on next 10m maxsize 10240m;

Tablespace created.

SQL> create table t_xifenfei tablespace xifenfei
  2  as
  3  select * from dba_objects;

Table created.

SQL> insert into t_xifenfei
  2  select * from dba_objects;

30803 rows created.

SQL> commit;

Commit complete.

SQL> alter system checkpoint;

System altered.

RMAN> backup tablespace xifenfei format '/tmp/no_truncate_xifenfei';

SQL> truncate table t_xifenfei;

Table truncated.

[oracle@xifenfei ~]$ ls -l /tmp/*truncate_xifenfei
-rw-r-----  1 oracle oinstall 7004160 Aug 26 22:52 /tmp/no_truncate_xifenfei
-rw-r-----  1 oracle oinstall 7004160 Aug 26 22:53 /tmp/truncate_xifenfei