今天来模拟一个非归档模式下恢复OFFLINE数据文件的场景，主要有2种情况： 一种是在线日志没有被覆盖，另一种是在线日志被覆盖。 第一种情况比较简单，数据库自身就能处理，而第二种情况稍显复杂，但也并不难，下面开始整个实验过程： 一、在线日志没有被覆盖
今天来模拟一个非归档模式下恢复OFFLINE数据文件的场景，主要有2种情况：
一种是在线日志没有被覆盖，另一种是在线日志被覆盖。
第一种情况比较简单，数据库自身就能处理，而第二种情况稍显复杂，但也并不难，下面开始整个实验过程：
一、在线日志没有被覆盖的场景
--切换数据库到非归档模式
SQL> archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 6
Next log sequence to archive 8
Current log sequence 8
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.
Total System Global Area 285212672 bytes
Fixed Size 1218992 bytes
Variable Size 125830736 bytes
Database Buffers 155189248 bytes
Redo Buffers 2973696 bytes
Database mounted.
SQL> alter database noarchivelog;
Database altered.
SQL> archive log list
Database log mode No Archive Mode
Automatic archival Disabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 6
Current log sequence 8
SQL>
--创建测试环境(创建表空间，创建用户，创建测试表，插入数据)
SQL> create tablespace zlm_test datafile '/u01/app/oracle/oradata/ora10g/zlm_test01.dbf' size 50M;
Tablespace created.
SQL> create user zlm1 identified by oracle;
User created.
SQL> grant connect,resource to zlm1;
Grant succeeded.
SQL> alter user zlm1 default tablespace zlm_test;
User altered.
SQL> conn zlm1/oracle
Connected.
SQL> create table offline_test(id int,name varchar2(10));
Table created.
SQL> insert into offline_test values(1,'aaron8219');
1 row created.
SQL> commit;
Commit complete.
--查看数据文件检查点SCN
SQL> set line 130
SQL> col name for a45
SQL> select file#,name,status,checkpoint_change# from v$datafile order by 1;
FILE# NAME STATUS CHECKPOINT_CHANGE#
---------- --------------------------------------------- ------- ------------------
1 /u01/app/oracle/oradata/ora10g/system01.dbfSYSTEM 551520
2 /u01/app/oracle/oradata/ora10g/undotbs01.dbf ONLINE 551520
3 /u01/app/oracle/oradata/ora10g/sysaux01.dbfONLINE 551520
4 /u01/app/oracle/oradata/ora10g/users01.dbfONLINE 551520
5 /u01/app/oracle/oradata/ora10g/example01.dbf ONLINE 551520
6 /u01/app/oracle/oradata/ora10g/zlm01.dbfONLINE 551520
7 /u01/app/oracle/oradata/ora10g/zlm02.dbfONLINE 551520
8 /u01/app/oracle/oradata/ora10g/zlm_test01.dbfONLINE 551753
此时8号数据文件的checkpoint SCN是551753，比其他文件都biger，或者说newer
尽管刚才插入一行数据后已经commit过了，但db buffer cache并不一定会立即刷到磁盘文件，需要手动执行检查点
SQL> alter system checkpoint;
System altered.
SQL> select file#,name,status,checkpoint_change# from v$datafile order by 1;
FILE# NAME STATUS CHECKPOINT_CHANGE#
---------- --------------------------------------------- ------- ------------------
1 /u01/app/oracle/oradata/ora10g/system01.dbfSYSTEM 552134
2 /u01/app/oracle/oradata/ora10g/undotbs01.dbf ONLINE 552134
3 /u01/app/oracle/oradata/ora10g/sysaux01.dbfONLINE 552134
4 /u01/app/oracle/oradata/ora10g/users01.dbfONLINE 552134
5 /u01/app/oracle/oradata/ora10g/example01.dbf ONLINE 552134
6 /u01/app/oracle/oradata/ora10g/zlm01.dbfONLINE 552134
7 /u01/app/oracle/oradata/ora10g/zlm02.dbfONLINE 552134
8 /u01/app/oracle/oradata/ora10g/zlm_test01.dbf ONLINE 552134
--查看数据文件头的检查点SCN
SQL> select file#,name,status,checkpoint_change# from v$datafile_header order by 1;
FILE# NAME STATUS CHECKPOINT_CHANGE#
---------- --------------------------------------------- ------- ------------------
1 /u01/app/oracle/oradata/ora10g/system01.dbfONLINE 552134
2 /u01/app/oracle/oradata/ora10g/undotbs01.dbf ONLINE 552134
3 /u01/app/oracle/oradata/ora10g/sysaux01.dbfONLINE 552134
4 /u01/app/oracle/oradata/ora10g/users01.dbfONLINE 552134
5 /u01/app/oracle/oradata/ora10g/example01.dbf ONLINE 552134
6 /u01/app/oracle/oradata/ora10g/zlm01.dbfONLINE 552134
7 /u01/app/oracle/oradata/ora10g/zlm02.dbfONLINE 552134
8 /u01/app/oracle/oradata/ora10g/zlm_test01.dbf ONLINE 552134
执行了检查点以后，脏数据刷到磁盘数据文件，数据库全部数据文件的检查点SCN都会保持一致
--当前日志情况
SQL> select * from v$Log;
GROUP# THREAD# SEQUENCE# BYTES MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIME
---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- ----------
1 1 7 52428800 1 YES INACTIVE 551038 05-9? -14
2 1 8 52428800 1NO CURRENT 551097 05-9? -14
3 1 6 52428800 1 YES INACTIVE 550653 05-9? -14
--把8号数据文件OFFLINE
SQL> alter database datafile 8 offline; --只有归档模式可以用
alter database datafile 8 offline
*
ERROR at line 1:
ORA-01145: offline immediate disallowed unless media recovery enabled
SQL> alter database datafile 8 offline drop; --非归档要用offline drop，注意，不是真正的删除物理数据文件
Database altered.
SQL> alter database datafile 8 online; --offline drop以后，需要recover以后才能online
alter database datafile 8 online
*
ERROR at line 1:
ORA-01113: file 8 needs media recovery
ORA-01110: data file 8: '/u01/app/oracle/oradata/ora10g/zlm_test01.dbf'
SQL> recover datafile 8
Media recovery complete.
SQL> alter database datafile 8 online;
Database altered.
由于此时在线日志并没有被覆盖，可以进行recover操作，然后对8号数据文件进行online
二、在线日志被覆盖的场景
--把8号数据文件重新OFFLINE
SQL> alter database datafile 8 offline drop;
Database altered.
--查看在线日志当前状态
SQL> select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIME
---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- ----------
1 1 7 52428800 1 YES INACTIVE 551038 05-9? -14
2 1 8 52428800 1NO CURRENT 551097 05-9? -14
3 1 6 52428800 1 YES INACTIVE 550653 05-9? -14
--切换3次日志，把当前日志内容覆盖
SQL> alter system switch logfile;
System altered.
SQL> select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIME
---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- ----------
1 1 7 52428800 1 YES INACTIVE 551038 05-9? -14
2 1 8 52428800 1 NO ACTIVE 551097 05-9? -14
3 1 9 52428800 1NO CURRENT 552891 05-9? -14
SQL> alter system switch logfile;
System altered.
SQL> select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIME
---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- ----------
1 1 10 52428800 1NO CURRENT 552899 05-9? -14
2 1 8 52428800 1 NO ACTIVE 551097 05-9? -14
3 1 9 52428800 1 NO ACTIVE 552891 05-9? -14
SQL> alter system switch logfile;
System altered.
SQL> select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIME
---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- ----------
1 1 10 52428800 1 NO ACTIVE 552899 05-9? -14
2 1 11 52428800 1NO CURRENT 552911 05-9? -14
3 1 9 52428800 1 NO ACTIVE 552891 05-9? -14
当前日志的检查点SCN从551097变为552911，也就是说，第3次切换日志以后，current日志被覆盖了
--对8号数据文件online
SQL> alter database datafile 8 online;
alter database datafile 8 online
*
ERROR at line 1:
ORA-01113: file 8 needs media recovery
ORA-01110: data file 8: '/u01/app/oracle/oradata/ora10g/zlm_test01.dbf'
可以看到，同样是需要media recovery的，从以下视图可以获得同样地结果：
SQL> select file#,online_status from v$recover_file;
FILE# ONLINE_
---------- -------
8 OFFLINE
SQL> recover datafile 8
ORA-00279: change 552554 generated at 09/05/2014 12:16:56 needed for thread 1
ORA-00289: suggestion : /u01/app/oracle/flash_recovery_area/ORA10G/archivelog/2014_09_05/o1_mf_1_8_%u_.arc
ORA-00280: change 552554 for thread 1 is in sequence #8
Specify log: {
=suggested | filename | AUTO | CANCEL}
auto
ORA-00308: cannot open archived log '/u01/app/oracle/flash_recovery_area/ORA10G/archivelog/2014_09_05/o1_mf_1_8_%u_.arc'
ORA-27037: unable to obtain file status
Linux Error: 2: No such file or directory
Additional information: 3
ORA-00308: cannot open archived log '/u01/app/oracle/flash_recovery_area/ORA10G/archivelog/2014_09_05/o1_mf_1_8_%u_.arc'
ORA-27037: unable to obtain file status
Linux Error: 2: No such file or directory
Additional information: 3
SQL>
自动recover失败，原因是在线日志已经被覆盖了，而且目前是非归档模式，也没有可用的归档日志进行recover，
这个时候，数据库自身无法重新让该文件再online了，必须借助一个特殊工具——BBED(Block Browse Editor)
BBED是Oracle仅供内部使用的一个数据块浏览编辑工具，通过命令行方式，对数据块所在磁盘文件的十六进制物理地址进行修改，主要用来处理一些特殊恢复的场景(无备份恢复方式)。
BBED在10g数据库软件中是自带的，但是需要对其进行编译安装，需要用到3个包，分别是sbbdpt.o、ssbbded.o、bbedus.msb，其中sbbdpt.o、ssbbded.o位于?/rdbms/lib下，而bbedus.msb位于?/rdbms/mesg下。据说由于在DBLINK场景中使用BBED修改数据块的SCN，会引起SCN headroom，因此在11g中，默认没有放入这几个文件(Oracle也许并不愿意让客户使用BBED )，因此如果11g中要使用BBED，需要去10g数据库中手工拷贝这3个文件到相应位置，然后再编译安装，要注意的是，BBED的32bit和64bit文件不能互用。似乎只能用于Unix/Linux系统中。
--检查BBED所需的3个文件sbbdpt.o、ssbbded.o、bbedus.msb是否存在
SQL> !
[oracle@ora10g ~]$ cd $ORACLE_HOME/rdbms/lib
[oracle@ora10g lib]$ ll
...
-rwxr-xr-x 1 oracle oinstall 3043 Jun 28 2005 sbbdpt.o
-rwxr-xr-x 1 oracle oinstall 2721 Jun 28 2005 ssbbded.o
...
[oracle@ora10g lib]$ cd $ORACLE_HOME/rdbms/mesg/
[oracle@ora10g mesg]$ ll
-rwxr-xr-x 1 oracle oinstall 8704 Jun 28 2005 bbedus.msb
...
--编译安装BBED
[oracle@ora10g mesg]$ make -f $ORACLE_HOME/rdbms/lib/ins_rdbms.mk BBED=$ORACLE_HOME/bin/bbed $ORACLE_HOME/bin/bbed
Linking BBED utility (bbed)
rm -f /u01/app/oracle/product/10.2.0/db_1/bin/bbed
gcc -o /u01/app/oracle/product/10.2.0/db_1/bin/bbed -L/u01/app/oracle/product/10.2.0/db_1/rdbms/lib/ -L/u01/app/oracle/product/10.2.0/db_1/lib/ -L/u01/app/oracle/product/10.2.0/db_1/lib/stubs/ -L/usr/lib -lirc /u01/app/oracle/product/10.2.0/db_1/lib/s0main.o /u01/app/oracle/product/10.2.0/db_1/rdbms/lib/ssbbded.o /u01/app/oracle/product/10.2.0/db_1/rdbms/lib/sbbdpt.o `cat /u01/app/oracle/product/10.2.0/db_1/lib/ldflags` -lnsslb10 -lncrypt10 -lnsgr10 -lnzjs10 -ln10 -lnnz10 -lnl10 /u01/app/oracle/product/10.2.0/db_1/rdbms/lib/defopt.o -ldbtools10 -lclntsh `cat /u01/app/oracle/product/10.2.0/db_1/lib/ldflags` -lnsslb10 -lncrypt10 -lnsgr10 -lnzjs10 -ln10 -lnnz10 -lnl10 -lnro10 `cat /u01/app/oracle/product/10.2.0/db_1/lib/ldflags` -lnsslb10 -lncrypt10 -lnsgr10 -lnzjs10 -ln10 -lnnz10 -lnl10 -lclient10 -lnnetd10 -lvsn10 -lcommon10 -lgeneric10 -lmm -lsnls10 -lnls10 -lcore10 -lsnls10 -lnls10 -lcore10 -lsnls10 -lnls10 -lxml10 -lcore10 -lunls10 -lsnls10 -lnls10 -lcore10 -lnls10 `cat /u01/app/oracle/product/10.2.0/db_1/lib/ldflags` -lnsslb10 -lncrypt10 -lnsgr10 -lnzjs10 -ln10 -lnnz10 -lnl10 -lnro10 `cat /u01/app/oracle/product/10.2.0/db_1/lib/ldflags` -lnsslb10 -lncrypt10 -lnsgr10 -lnzjs10 -ln10 -lnnz10 -lnl10 -lclient10 -lnnetd10 -lvsn10 -lcommon10 -lgeneric10 -lsnls10 -lnls10 -lcore10 -lsnls10 -lnls10 -lcore10 -lsnls10 -lnls10 -lxml10 -lcore10 -lunls10 -lsnls10 -lnls10 -lcore10 -lnls10 -lclient10 -lnnetd10 -lvsn10 -lcommon10 -lgeneric10 -lsnls10 -lnls10 -lcore10 -lsnls10 -lnls10 -lcore10 -lsnls10 -lnls10 -lxml10 -lcore10 -lunls10 -lsnls10 -lnls10 -lcore10 -lnls10 `cat /u01/app/oracle/product/10.2.0/db_1/lib/sysliblist` -Wl,-rpath,/u01/app/oracle/product/10.2.0/db_1/lib -lm `cat /u01/app/oracle/product/10.2.0/db_1/lib/sysliblist` -ldl -lm -L/u01/app/oracle/product/10.2.0/db_1/lib
--首先用下面的SQL语句获得数据文件列表
SQL> select file#||' '||name||' '||bytes from v$datafile ;
FILE#||''||NAME||''||BYTES
--------------------------------------------------------------------------------
1 /u01/app/oracle/oradata/ora10g/system01.dbf 524288000
2 /u01/app/oracle/oradata/ora10g/undotbs01.dbf 31457280
3 /u01/app/oracle/oradata/ora10g/sysaux01.dbf 251658240
4 /u01/app/oracle/oradata/ora10g/users01.dbf 104857600
5 /u01/app/oracle/oradata/ora10g/example01.dbf 104857600
6 /u01/app/oracle/oradata/ora10g/zlm01.dbf 104857600
7 /u01/app/oracle/oradata/ora10g/zlm02.dbf 104857600
8 /u01/app/oracle/oradata/ora10g/zlm_test01.dbf 52428800
--创建LISTFILE
SQL> !
[oracle@ora10g ~]$ touch bbedlistfile.log --扩展名任意，能被parfile识别到就可以
[oracle@ora10g ~]$ cat >> bbedlistfile.log
> 1 /u01/app/oracle/oradata/ora10g/system01.dbf 524288000
> 2 /u01/app/oracle/oradata/ora10g/undotbs01.dbf 31457280
> 3 /u01/app/oracle/oradata/ora10g/sysaux01.dbf 251658240
> 4 /u01/app/oracle/oradata/ora10g/users01.dbf 104857600
> 5 /u01/app/oracle/oradata/ora10g/example01.dbf 104857600
> 6 /u01/app/oracle/oradata/ora10g/zlm01.dbf 104857600
> 7 /u01/app/oracle/oradata/ora10g/zlm02.dbf 104857600
> 8 /u01/app/oracle/oradata/ora10g/zlm_test01.dbf 52428800
> EOF
--创建PARFILE
[oracle@ora10g ~]$ touch parfile.bbd --注意扩展名为bbd，否则识别不了
[oracle@ora10g ~]$ cat >> parfile.bbd
> blocksize=8192
> listfile=bbedlistfile.log
> mode=edit
> EOF
--查看装载到BBED中的文件信息
BBED> info
File# Name Size(blks)
----- ---- ----------
1 /u01/app/oracle/oradata/ora10g/system01.dbf 64000
2 /u01/app/oracle/oradata/ora10g/undotbs01.dbf 3840
3 /u01/app/oracle/oradata/ora10g/sysaux01.dbf 30720
4 /u01/app/oracle/oradata/ora10g/users01.dbf 12800
5 /u01/app/oracle/oradata/ora10g/example01.dbf 12800
6 /u01/app/oracle/oradata/ora10g/zlm01.dbf 12800
7 /u01/app/oracle/oradata/ora10g/zlm02.dbf 12800
8 /u01/app/oracle/oradata/ora10g/zlm_test01.dbf 6400
--进入BBED命令行模式(默认密码：blockedit)
[oracle@ora10g ~]$ bbed parfile=parfile.bbd
Password:
BBED: Release 2.0.0.0.0 - Limited Production on Fri Sep 5 13:09:55 2014
Copyright (c) 1982, 2005, Oracle. All rights reserved.
************* !!! For Oracle Internal Use only !!! ***************
BBED>
注意：这里使用了指定了参数文件和文件列表方式登陆BBED，否则，所有参数都需要在BBED的CML界面中输入
如果数据库做过resetlogs，那么需要关注以下两项：
kcvfhrls
kcvfhrlc
由于这里并没有用resetlogs打开数据库，所以只需关注以下几项值：
kscnbas
kcvcptim
kcvfhcpc
kcvfhccc
--查看datafile 8的信息
BBED> set file 8
FILE# 8
BBED> p kcvfhckp
struct kcvfhckp, 36 bytes @484
struct kcvcpscn, 8 bytes @484
ub4 kscnbas @484 0x00086e6a --数据文件头的SCN
ub2 kscnwrp @488 0x0000
ub4 kcvcptim @492 0x331c12b8
ub2 kcvcpthr @496 0x0001
union u, 12 bytes @500
struct kcvcprba, 12 bytes @500
ub4 kcrbaseq @500 0x00000008 --数据文件当前写的redolog sequence
ub4 kcrbabno @504 0x00000ab9 --数据文件当前写的redolog block number
ub2 kcrbabof @508 0x0010
ub1 kcvcpetb[0] @512 0x02
ub1 kcvcpetb[1] @513 0x00
ub1 kcvcpetb[2] @514 0x00
ub1 kcvcpetb[3] @515 0x00
ub1 kcvcpetb[4] @516 0x00
ub1 kcvcpetb[5] @517 0x00
ub1 kcvcpetb[6] @518 0x00
ub1 kcvcpetb[7] @519 0x00
BBED> p kcvfhcpc
ub4 kcvfhcpc @140 0x00000005
BBED> p kcvfhccc
ub4 kcvfhccc @148 0x00000004
--和datafile 7做比较
BBED> set file 7
FILE# 7
BBED> p kcvfhckp
struct kcvfhckp, 36 bytes @484
struct kcvcpscn, 8 bytes @484
ub4 kscnbas @484 0x00086fcf
ub2 kscnwrp @488 0x0000
ub4 kcvcptim @492 0x331c159d
ub2 kcvcpthr @496 0x0001
union u, 12 bytes @500
struct kcvcprba, 12 bytes @500
ub4 kcrbaseq @500 0x0000000b
ub4 kcrbabno @504 0x00000002
ub2 kcrbabof @508 0x0010
ub1 kcvcpetb[0] @512 0x02
ub1 kcvcpetb[1] @513 0x00
ub1 kcvcpetb[2] @514 0x00
ub1 kcvcpetb[3] @515 0x00
ub1 kcvcpetb[4] @516 0x00
ub1 kcvcpetb[5] @517 0x00
ub1 kcvcpetb[6] @518 0x00
ub1 kcvcpetb[7] @519 0x00
BBED> p kcvfhcpc
ub4 kcvfhcpc @140 0x0000001b
BBED> p kcvfhccc
ub4 kcvfhccc @148 0x0000001a
其实这里kcvfhcpc和kcvfhccc可以不必理会，要修改的就2个地方
只需要把datafile 8中offset 484和500的值改成和datafile 7一致，就ok了
--用dump命令查看datafile 7的存储值
BBED> dump /v offset 484 count 16
File: /u01/app/oracle/oradata/ora10g/zlm02.dbf (7)
Block: 1 Offsets: 484 to 499 Dba:0x01c00001
-------------------------------------------------------
cf6f0800 0000f1b7 9d151c33 01000000 l ?....穹...3....
注意，这里存储的格式与之前通过p kcvfhckp查看到的值是相反的
--通过以下视图可以获得endian值：
SQL> set lin 130
SQL> col platform_name for a40
SQL> select platform_id,platform_name,endian_format from v$db_transportable_platform;
PLATFORM_ID PLATFORM_NAME ENDIAN_FORMAT
----------- ---------------------------------------- --------------
7 Microsoft Windows IA (32-bit) Little
10 Linux IA (32-bit) Little
5 HP Tru64 UNIX Little
11 Linux IA (64-bit) Little
15 HP Open VMS Little
8 Microsoft Windows IA (64-bit) Little
13 Linux 64-bit for AMD Little
12 Microsoft Windows 64-bit for AMD Little
17 Solaris Operating System (x86) Little
Big-Endian和Little-Endian的定义如下：
a) Little-Endian 低位字节排放在内存的低地址端，高位字节排放在内存的高地址端。
b) Big-Endian 高位字节排放在内存的低地址端，低位字节排放在内存的高地址端。
BBED> dump /v offset 500 count 16
File: /u01/app/oracle/oradata/ora10g/zlm02.dbf (7)
Block: 1 Offsets: 500 to 515 Dba:0x01c00001
-------------------------------------------------------
0b000000 02000000 1000e1bf 02000000 l ..........峥....
BBED> modify /x cf6f0800 dba 8,1 offset 484
BBED-00209: invalid number (cf6f0800)
要修改的值为8位4字节十六进制，一起写会提示非法值，可以先修改前3个字节
BBED> modify /x cf6f08 dba 8,1 offset 484
Warning: contents of previous BIFILE will be lost. Proceed? (Y/N) y
File: /u01/app/oracle/oradata/ora10g/zlm_test01.dbf (8)
Block: 1 Offsets: 484 to 499 Dba:0x02000001
------------------------------------------------------------------------
cf6f0800 00000000 b8121c33 01000000
--再次验证一下
BBED> d /v dba 8,1 offset 484 count 16 --d就是dump，m就是modify，BBED的命令可以用首字母缩写
File: /u01/app/oracle/oradata/ora10g/zlm_test01.dbf (8)
Block: 1 Offsets: 484 to 499 Dba:0x02000001
-------------------------------------------------------
cf6f0800 00000000 b8121c33 01000000 l ?......?.3....
BBED> set file 7 block 1 --注意，这里必须再次指定一下file和block，刚才修改完以后默认file是8号
FILE# 7
BLOCK# 1
BBED> d /v offset 500 count 16
File: /u01/app/oracle/oradata/ora10g/zlm02.dbf (7)
Block: 1 Offsets: 500 to 515 Dba:0x01c00001
-------------------------------------------------------
0b000000 02000000 1000e1bf 02000000 l ..........峥....
BBED> m /x 0b dba 8,1 offset 500
File: /u01/app/oracle/oradata/ora10g/zlm_test01.dbf (8)
Block: 1 Offsets: 500 to 515 Dba:0x02000001
------------------------------------------------------------------------
0b000000 b90a0000 1000bf0e 02000000
BBED> sum
Check value for File 8, Block 1:
current = 0xf66e, required = 0xf7c8
BBED> sum apply -执行该命令才算是真正的修改完成
Check value for File 8, Block 1:
current = 0xf7c8, required = 0xf7c8
BBED> exit
[oracle@ora10g ~]$ sqlplus / as sysdba
SQL*Plus: Release 10.2.0.1.0 - Production on Fri Sep 5 13:49:58 2014
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options
SQL> select file#,checkpoint_change#,last_change# from v$datafile;
FILE# CHECKPOINT_CHANGE# LAST_CHANGE#
---------- ------------------ ------------
1 552911
2 552911
3 552911
4 552911
5 552911
6 552911
7 552911
8 552554 552828
SQL> select file#,checkpoint_change#,resetlogs_change# from v$datafile_header;
FILE# CHECKPOINT_CHANGE# RESETLOGS_CHANGE#
---------- ------------------ -----------------
1 552911547304
2 552911547304
3 552911547304
4 552911547304
5 552911547304
6 552911547304
7 552911547304
8 552911547304
虽然8号数据文件的checkpoint_change#，last_change#与其他文件还是不一致的，但是它的数据文件头中的信息已经一致了，也就是我们刚才改的内容
--recover数据文件并使其online
SQL> recover datafile 8
Media recovery complete.
QL> alter database datafile 8 online;
Database altered.
--再次查看
SQL> select file#,checkpoint_change#,last_change# from v$datafile;
FILE# CHECKPOINT_CHANGE# LAST_CHANGE#
---------- ------------------ ------------
1 552911
2 552911
3 552911
4 552911
5 552911
6 552911
7 552911
8 555977
SQL> select file#,checkpoint_change#,resetlogs_change# from v$datafile_header;
FILE# CHECKPOINT_CHANGE# RESETLOGS_CHANGE#
---------- ------------------ -----------------
1 552911 547304
2 552911 547304
3 552911 547304
4 552911 547304
5 552911 547304
6 552911 547304
7 552911 547304
8 555977 547304
SQL> select * from zlm1.offline_test;
ID NAME
---------- ----------
1 aaron8219
此时可以看到，虽然8号数据文件的checkpoint_change#仍然是不一致的，但是已经比其他文件newer了，说明是当前更改的文件，其实之前不能直接online，就是因为8号数据文件的checkpoint_change#=552554要比其他文件的checkpoint_change#552911要older所致。online的时候，控制文件中记录的信息过旧(因为之前文件是offline的，它的checkpoint信息自那一刻开始就不会再变化)，需要用recover把它推送到其他文件的checkpoint之后的值(即比它们都要biger or newer)。经过recover以后，我们获得了8号文件新的checkpoint_change#=555977>552911，因此才能够重新将它online，即通过BBED，手工修改数据文件头中的checkpoint SCN，使其能够不依赖于online redo logfile和archive logfile，就能实现recover操作。
SQL> alter system checkpoint;
System altered.
SQL> select file#,checkpoint_change#,last_change# from v$datafile;
FILE# CHECKPOINT_CHANGE# LAST_CHANGE#
---------- ------------------ ------------
1 556048
2 556048
3 556048
4 556048
5 556048
6 556048
7 556048
8 556048
8 rows selected.
SQL> select file#,checkpoint_change#,resetlogs_change# from v$datafile_header;
FILE# CHECKPOINT_CHANGE# RESETLOGS_CHANGE#
---------- ------------------ -----------------
1 556048 547304
2 556048 547304
3 556048 547304
4 556048 547304
5 556048 547304
6 556048 547304
7 556048 547304
8 556048 547304
8 rows selected.
SQL>
当我们再次手工执行检查点以后，就会触发DBWR进程把DB BUFFER CACHE中的脏数据写到磁盘文件，此时8号数据文件和数据文件头中的checkpoint SCN信息，已经与其他数据文件都一致了。至此，整个恢复过程顺利结束。
总结
本例是通过Oracle BBED工具，在非归档模式下对OFFLINE数据文件进行恢复的过程。注意，由于current日志非常重要，它仅保留在内存中(SGA的db buffer cache)，所以一般重要的系统，都是需要开启归档的，这样可以保证current日志被覆盖后依然可以对数据文件进行前滚(recover)。当我们既没有current日志，又没有归档日志，那就只能通过特殊手段来进行恢复了。如果OFFLINE的数据文件中有比较重要的数据内容，就能够使其重新ONLINE并取出数据了。当然，BBED还有更多比较复杂的运用，如当某个数据文件块出现损坏，又没有可以用的备份时，通过BBED，可以对数据文件块直接dump并替换内容等，这里就暂且不讨论了，大家可以自己参考手册进行研究。总得来说，BBED还是比较inernal的东东，想要掌握周全，实属不易。
