[20190124]bbed恢復資料遇到延遲塊清除的問題.txt

--//最近使用bbed做一個恢復測試,遇到一個問題.以前我的測試如果修改刪除flag從0x3c=>0x2c,sum apply後,使用verify提示類似如下:

BBED> verify

DBVERIFY - Verification starting

FILE = /mnt/ramdisk/book/users01.dbf

BLOCK = 523

Block Checking: DBA = 16777739, Block Type = KTB-managed data block

data header at 0x7fddbce4127c

kdbchk: the amount of space used is not equal to block size

used=44 fsc=9 avsp=8020 dtl=8064

Block 523 failed with check code 6110

--//如果偷懶,可以跳過這步.但是如果遇到提交時資料塊不在快取或者更新涉及的塊太多,可能會出現許多塊不做塊清除,oracle執行的是

--//快速塊清除操作.這樣一些塊在下一次touch時才修改對應ITL操以及對應記錄的lock資訊才會更新.

--//對於這樣的塊,恢復時恢復會遇到什麼問題呢?透過例子說明問題.

1.環境:

SCOTT@book> @ 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.建立測試環境:

SCOTT@book> create table t as select rownum id,'test' name from dual connect by level<=2;

Table created.

SCOTT@book> select rowid,t.* from t;

ROWID ID NAME

------------------ ---------- --------------------

AAAWPYAAEAAAAILAAA 1 test

AAAWPYAAEAAAAILAAB 2 test

SCOTT@book> @ rowid AAAWPYAAEAAAAILAAA

OBJECT FILE BLOCK ROW ROWID_DBA DBA TEXT

---------- ---------- ---------- ---------- -------------------- -------------------- ----------------------------------------

91096 4 523 0 0x100020B 4,523 alter system dump datafile 4 block 523 ;

SCOTT@book> delete from t where id=1;

1 row deleted.

SCOTT@book> alter system flush buffer_cache;

System altered.

SCOTT@book> alter system flush buffer_cache;

System altered.

--//注:一定要確定對於資料塊資訊已經重新整理到磁碟.IMU環境有時候奇怪,髒塊有時候也不會寫盤.

SYS@book> @ bh 4 523

HLADDR DBARFIL DBABLK CLASS CLASS_TYPE STATE TCH CR_SCN_BAS CR_SCN_WRP CR_UBA_FIL CR_UBA_BLK CR_UBA_SEQ BA OBJECT_NAME

---------------- ------- ------ ----- ---------- ----- --- ---------- ---------- ---------- ---------- ---------- ---------------- -----------

000000008538CA18 4 523 1 data block free 0 0 0 0 0 0 0000000073D1C000 T

000000008538CA18 4 523 1 data block free 0 0 0 0 0 0 0000000073D22000 T

SCOTT@book> commit ;

Commit complete.

3.使用bbed恢復看看:

BBED> set dba 4,523

DBA 0x0100020b (16777739 4,523)

BBED> x /rnc *kdbr[0]

rowdata[11] @8177

-----------

flag@8177: 0x3c (KDRHFL, KDRHFF, KDRHFD, KDRHFH)

lock@8178: 0x02

cols@8179: 0

--//使用ITL槽2.看看ITL槽2(從0開始)的情況:

BBED> p ktbbh.ktbbhitl[1]

struct ktbbhitl[1], 24 bytes @68

struct ktbitxid, 8 bytes @68

ub2 kxidusn @68 0x000a

ub2 kxidslt @70 0x0013

ub4 kxidsqn @72 0x00005816

struct ktbituba, 8 bytes @76

ub4 kubadba @76 0x00c0028e

ub2 kubaseq @80 0x10d5

ub1 kubarec @82 0x0f

ub2 ktbitflg @84 0x0001 (NONE)

union _ktbitun, 2 bytes @86

sb2 _ktbitfsc @86 9

ub2 _ktbitwrp @86 0x0009

ub4 ktbitbas @88 0x00000000

--//可以發現ktbitflg=0x0001,表示沒有提交.ktbitbas=0x00000000,也就是沒有scn相關資訊寫入.

BBED> assign offset 8177=0x2c;

Warning: contents of previous BIFILE will be lost. Proceed? (Y/N) y

ub1 rowdata[0] @8177 0x2c

BBED> x /rnc *kdbr[0]

rowdata[11] @8177

-----------

flag@8177: 0x2c (KDRHFL, KDRHFF, KDRHFH)

lock@8178: 0x02

cols@8179: 2

col 0[2] @8180: 1

col 1[4] @8183: Test

BBED> sum apply

Check value for File 4, Block 523:

current = 0xdcbe, required = 0xdcbe

BBED> verify

DBVERIFY - Verification starting

FILE = /mnt/ramdisk/book/users01.dbf

BLOCK = 523

Block Checking: DBA = 16777739, Block Type = KTB-managed data block

data header at 0x7fddbce4127c

kdbchk: the amount of space used is not equal to block size

used=44 fsc=9 avsp=8020 dtl=8064

Block 523 failed with check code 6110

--//我以前測試提到過這樣恢復,讀取是沒有問題,雖然verify時包如上的錯誤.

SCOTT@book> alter system flush buffer_cache;

System altered.

SCOTT@book> select rowid,t.* from t;

ROWID ID NAME

------------------ ---------- --------------------

AAAWPZAAEAAAAILAAA 1 Test

AAAWPZAAEAAAAILAAB 2 Test

SCOTT@book> alter system flush buffer_cache;

System altered.

BBED> x /rnc dba 4,523 *kdbr[0]

rowdata[11] @8177

-----------

flag@8177: 0x2c (KDRHFL, KDRHFF, KDRHFH)

lock@8178: 0x00

cols@8179: 2

col 0[2] @8180: 1

col 1[4] @8183: Test

BBED> p dba 4,523 ktbbh.ktbbhitl[1]

struct ktbbhitl[1], 24 bytes @68

struct ktbitxid, 8 bytes @68

ub2 kxidusn @68 0x000a

ub2 kxidslt @70 0x0013

ub4 kxidsqn @72 0x00005816

struct ktbituba, 8 bytes @76

ub4 kubadba @76 0x00c0028e

ub2 kubaseq @80 0x10d5

ub1 kubarec @82 0x0f

ub2 ktbitflg @84 0xa000 (KTBFUPB, KTBFCOM)

union _ktbitun, 2 bytes @86

sb2 _ktbitfsc @86 3

ub2 _ktbitwrp @86 0x0003

ub4 ktbitbas @88 0x1774676a

--//OK,可以發現沒有問題.即使現在還報錯:

BBED> verify dba 4,523

DBVERIFY - Verification starting

FILE = /mnt/ramdisk/book/users01.dbf

BLOCK = 523

Block Checking: DBA = 16777739, Block Type = KTB-managed data block

data header at 0x13efe7c

kdbchk: the amount of space used is not equal to block size

used=44 fsc=0 avsp=8029 dtl=8064

Block 523 failed with check code 6110

--//如果使用system表空間呢?下一篇測試看看.

[20190124]bbed恢復資料遇到延遲塊清除的問題.txt

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