[20171115]恢复数据文件块头3补充.txt
--// 昨天做了恢复数据文件块头,通过备份文件直接取出文件块头,覆盖原来的数据块,然后修复.
--//补充几点:
--1.文件头损坏,无法使用rman的块恢复功能.
--2.文件头损坏,dbv检查发现都是坏块.我感觉主要文件块头损坏,dbv无法定位其它剩下的块.
1.环境:
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
2.建立测试环境:
CREATE TABLESPACE TEA DATAFILE
'/mnt/ramdisk/book/tea01.dbf' SIZE 40M AUTOEXTEND ON NEXT 16M MAXSIZE UNLIMITED
LOGGING
ONLINE
EXTENT MANAGEMENT LOCAL AUTOALLOCATE
BLOCKSIZE 8K
SEGMENT SPACE MANAGEMENT AUTO
FLASHBACK ON;
create table t1 tablespace tea as select rownum id ,lpad('A',32,'A') name from dual connect by level<=1e5;
--//建立rman备份:
backup database filesperset=1 format '/home/oracle/backup/20171114_%U';
--//注:这是我个人主张的备份方式设置filesperset=1,可惜我们团队一直不建议使用.这样备份文件显得太多了.实际上这样做与我后面的恢复有关.
create table t2 tablespace tea as select rownum id ,lpad('B',32,'B') name from dual connect by level<=1e5;
--//建立大小5M的表。注:说明一点,我是先做数据库备份,再建立t2表.
--//破坏数据文件头,注:数据文件头在数据文件的第2块.第1块OS头.
update t2 set name=lpad('C',32,'C') where id <=5;
alter system checkpoint;
alter system checkpoint;
alter system checkpoint;
rollback ;
update t2 set name=lpad('D',32,'D') where id between 5 and 9;
commit ;
alter database datafile 6 offline ;
$ dd if=/dev/zero of=/mnt/ramdisk/book/tea01.dbf count=1 bs=8192 conv=notrunc seek=1
1+0 records in
1+0 records out
8192 bytes (8.2 kB) copied, 3.8338e-05 seconds, 214 MB/s
--//再次提醒不要忘记conv=notrunc参数,不然数据文件会被截断.我自己在以前测试中遇到这种情况!!
--//在以前rman备份的疑问中发现rman会修改块的信息,比如:
rdba_kcbh,spare3_kcbh,tailchk,当然还包括检查和.
--//拿当时备份的一个数据块分析:
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
SCOTT@book> select rowid,t1.* from t1 where id=100000;
ROWID ID NAME
------------------ ---------- ---------------------------------
AAAWITAAGAAAALSACM 100000 AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
SCOTT@book> select count(*) from t1 where rowid between 'AAAWITAAGAAAALSAAA' and 'AAAWITAAGAAAALSBBB';
COUNT(*)
----------
141
SCOTT@book> @ &r/rowid AAAWITAAGAAAALSACM
OBJECT FILE BLOCK ROW ROWID_DBA DBA TEXT
---------- ---------- ---------- ---------- -------------------- -------------------- ----------------------------------------
90643 6 722 140 0x18002D2 6,722 alter system dump datafile 6 block 722 ;
--//这个块仅仅141条记录.
$ cat filelist.txt
4 /mnt/ramdisk/book/users01.dbf
1 /mnt/ramdisk/book/system01.dbf
2 /mnt/ramdisk/book/sysaux01.dbf
3 /mnt/ramdisk/book/undotbs01.dbf
5 /mnt/ramdisk/book/example01.dbf
6 /mnt/ramdisk/book/tea01.dbf
100 /home/oracle/backup/20171114_fcsji7ti_1_1
BBED> map dba 100,723
File: /home/oracle/backup/20171114_fcsji7ti_1_1 (100)
Block: 723 Dba:0x190002d3
------------------------------------------------------------
KTB Data Block (Table/Cluster)
struct kcbh, 20 bytes @0
struct ktbbh, 96 bytes @20
struct kdbh, 14 bytes @116
struct kdbt[1], 4 bytes @130
sb2 kdbr[141] @134
ub1 freespace[1994] @416
ub1 rowdata[5778] @2410
ub4 tailchk @8188
--//备份集合
BBED> set dba 100,723
DBA 0x190002d3 (419431123 100,723)
BBED> p dba 100,723 kcbh.rdba_kcbh
ub4 rdba_kcbh @4 0x018002d3
BBED> p dba 100,723 kcbh.spare3_kcbh
ub2 spare3_kcbh @18 0x0001
BBED> p dba 100,723 tailchk
ub4 tailchk @8188 0x73fd06d2
--//数据块
BBED> set dba 6,722
DBA 0x018002d2 (25166546 6,722)
BBED> p dba 6,722 kcbh.rdba_kcbh
ub4 rdba_kcbh @4 0x018002d2
BBED> p dba 6,722 kcbh.spare3_kcbh
ub2 spare3_kcbh @18 0x0000
BBED> p dba 6,722 tailchk
ub4 tailchk @8188 0x73fd0602
--//可以看出备份修改kcbh.spare3_kcbh=0x0001,rdba_kcbh修改为备份块的rdba地址,把原来rdba地址的低2位保存在tailchk.
--//我这里备份集合块与数据块差别不大,如果差距很大会出现什么情况呢?
3.继续测试:
--// drop T1,这样前面就空出一段空间没有使用,rman备份也不会备份这些块.在看看这个备份文件.
--//分析前准备:
1.记下表T2 id=1e5在那个数据块:
SCOTT@book> drop table t1 purge;
Table dropped.
SCOTT@book> select rowid,t2.* from t2 where id=1e5;
ROWID ID NAME
------------------ ---------- ---------------------------------
AAAWIUAAGAAAAVSACM 100000 BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
SCOTT@book> @ &r/rowid AAAWIUAAGAAAAVSACM
OBJECT FILE BLOCK ROW ROWID_DBA DBA TEXT
---------- ---------- ---------- ---------- -------------------- -------------------- ----------------------------------------
90644 6 1362 140 0x1800552 6,1362 alter system dump datafile 6 block 1362
SCOTT@book> select count(*) from t2 where rowid between 'AAAWIUAAGAAAAVSAAA' and 'AAAWIUAAGAAAAVSACM';
COUNT(*)
----------
141
--//说明该块有141条记录.
2.使用rman备份数据文件6:
RMAN> backup datafile 6 format '/home/oracle/backup/datafile6_20171115_%U' ;
Starting backup at 2017-11-15 15:42:38
using channel ORA_DISK_1
using channel ORA_DISK_2
using channel ORA_DISK_3
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00006 name=/mnt/ramdisk/book/tea01.dbf
channel ORA_DISK_1: starting piece 1 at 2017-11-15 15:42:38
channel ORA_DISK_1: finished piece 1 at 2017-11-15 15:42:39
piece handle=/home/oracle/backup/datafile6_20171115_fqsjku7e_1_1 tag=TAG20171115T154238 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
Finished backup at 2017-11-15 15:42:39
Starting Control File and SPFILE Autobackup at 2017-11-15 15:42:39
piece handle=/u01/app/oracle/fast_recovery_area/BOOK/autobackup/2017_11_15/o1_mf_s_960133359_f0qvzhdt_.bkp comment=NONE
Finished Control File and SPFILE Autobackup at 2017-11-15 15:42:40
--//备份文件=/home/oracle/backup/datafile6_20171115_fqsjku7e_1_1
BBED> info
File# Name Size(blks)
----- ---- ----------
1 /mnt/ramdisk/book/system01.dbf 0
2 /mnt/ramdisk/book/sysaux01.dbf 0
3 /mnt/ramdisk/book/undotbs01.dbf 0
4 /mnt/ramdisk/book/users01.dbf 0
5 /mnt/ramdisk/book/example01.dbf 0
6 /mnt/ramdisk/book/tea01.dbf 0
206 /home/oracle/backup/datafile6_20171115_fqsjku7e_1_1 0
$ ls -l /home/oracle/backup/datafile6_20171115_fqsjku7e_1_1
-rw-r----- 1 oracle oinstall 5980160 2017-11-15 15:42:38 /home/oracle/backup/datafile6_20171115_fqsjku7e_1_1
--//备份不到6M.
--//占用5980160/8192=730块.最大块号729(从0开始记数).
--//前面测试已经说明728备份的文件头.依次往前面看.
BBED> map dba 206,728
File: /home/oracle/backup/datafile6_20171115_fqsjku7e_1_1 (206)
Block: 728 Dba:0x338002d8
------------------------------------------------------------
Data File Header
struct kcvfh, 860 bytes @0
ub4 tailchk @8188
--OK,判断正确.
BBED> map dba 206,724
File: /home/oracle/backup/datafile6_20171115_fqsjku7e_1_1 (206)
Block: 724 Dba:0x338002d4
------------------------------------------------------------
KTB Data Block (Table/Cluster)
struct kcbh, 20 bytes @0
struct ktbbh, 96 bytes @20
struct kdbh, 14 bytes @116
struct kdbt[1], 4 bytes @130
sb2 kdbr[141] @134
ub1 freespace[1994] @416
ub1 rowdata[5778] @2410
ub4 tailchk @8188
BBED> set dba 206,724
DBA 0x338002d4 (864027348 206,724)
BBED> x /rnc *kdbr[140] dba 206,724
rowdata[0] @2410
----------
flag@2410: 0x2c (KDRHFL, KDRHFF, KDRHFH)
lock@2411: 0x00
cols@2412: 2
col 0[2] @2413: 100000
col 1[32] @2416: BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
--//说明判断正确,就是这块.
--//备份文件中块724对于就是dba=6,1362的备份.对比备份与对于数据块的不同:
p dba 6,1362 kcbh.rdba_kcbh
p dba 6,1362 kcbh.spare3_kcbh
p dba 6,1362 tailchk
p dba 206,724 kcbh.rdba_kcbh
p dba 206,724 kcbh.spare3_kcbh
p dba 206,724 tailchk
--//数据块
BBED> p dba 6,1362 kcbh.rdba_kcbh
ub4 rdba_kcbh @4 0x01800552
BBED> p dba 6,1362 kcbh.spare3_kcbh
ub2 spare3_kcbh @18 0x0000
BBED> p dba 6,1362 tailchk
ub4 tailchk @8188 0x75570602
BBED> p dba 6,1362 kcbh.chkval_kcbh
ub2 chkval_kcbh @16 0x30c7
--//备份集
BBED> p dba 206,724 kcbh.rdba_kcbh
ub4 rdba_kcbh @4 0x018005d4
BBED> p dba 206,724 kcbh.spare3_kcbh
ub2 spare3_kcbh @18 0x0001
BBED> p dba 206,724 tailchk
ub4 tailchk @8188 0x75570652
BBED> p dba 206,724 kcbh.chkval_kcbh
ub2 chkval_kcbh @16 0x3010
--//kcbh.spare3_kcbh 从 0x0000 => 0x0001.
--724=0x2d4
--1362=0x552
--//注意看原数据块 kcbh.rdba_kcbh=0x01800552 备份后变成了 kcbh.rdba_kcbh= 0x018005d4.
--//也就是将数据块的dba地址的低2位0x52保存到tailchk的低2位.
--//同时将备份时数据块的kcbh.rdba_kcbh的低2位0x52 变成备份块的块地址的低2位(前面0x02丢弃了)0xd4.
--//当然这样检查和也会发生变化.
--//将变化的低2位做异或操作.
$ echo 52 00 02 c7 d4 01 52 |xor.sh
52
00
02
C7
D4
01
52
xor result: 10
$ echo 0552 0000 0602 30c7 05d4 0001 0652 |xor.sh
0552
0000
0602
30C7
05D4
0001
0652
xor result: 3010
--//正好是备份对应块检查和的低2位.(dba 206,724 kcbh.chkval_kcbh=0x3010)
--//感觉自己好无聊^_^,放弃不再探究了.
--//关于做异或的脚本可以参考如下链接:
http://blog.itpub.net/267265/viewspace-2134945/
