最近在一個資料庫遇到了壞塊，以下是處理過程。

一、壞塊的發現及處理

[@more@]首先是在做RMAN備份的時候，看到alert檔案有壞塊報錯：
.......
Corrupt block relative dba: 0x00925026 (file 2, block 1200166)
Fractured block found during backing up datafile
Data in bad block:
type: 6 format: 2 rdba: 0x00925026
last change scn: 0x0578.15b7ebf7 seq: 0x1 flg: 0x06
spare1: 0x0 spare2: 0x0 spare3: 0x0
consistency value in tail: 0x33da0602
check value in block header: 0xf8d0
computed block checksum: 0xd82e
Reread of blocknum=1200166, file=+DATA/dwrac/datafile/dwdata_1m01.dbf. found same corrupt data
Reread of blocknum=1200166, file=+DATA/dwrac/datafile/dwdata_1m01.dbf. found same corrupt data
Reread of blocknum=1200166, file=+DATA/dwrac/datafile/dwdata_1m01.dbf. found same corrupt data
Reread of blocknum=1200166, file=+DATA/dwrac/datafile/dwdata_1m01.dbf. found same corrupt data
Reread of blocknum=1200166, file=+DATA/dwrac/datafile/dwdata_1m01.dbf. found same corrupt data
......

用dbv檢查也證實了這一點。

[oracle@dwdb02 admin]$ dbv file="+DATA/dwrac/datafile/dwdata_1m01.dbf" start=502554 end=1217134 userid=admin/sdoadmin123 blocksize=16384

DBVERIFY: Release 10.2.0.5.0 - Production on Thu Feb 17 14:50:13 2011

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

DBVERIFY - Verification starting : FILE = +DATA/dwrac/datafile/dwdata_1m01.dbf
Page 502554 is marked corrupt
Corrupt block relative dba: 0x0087ab1a (file 2, block 502554)
Bad header found during dbv:
Data in bad block:
type: 11 format: 2 rdba: 0x00800001
last change scn: 0x0000.00000000 seq: 0x1 flg: 0x04
spare1: 0x0 spare2: 0x0 spare3: 0x0
consistency value in tail: 0x00000b01
check value in block header: 0x85d8
computed block checksum: 0x0
......

DBVERIFY - Verification complete

Total Pages Examined : 714581
Total Pages Processed (Data) : 567369
Total Pages Failing (Data) : 0
Total Pages Processed (Index): 143342
Total Pages Failing (Index): 0
Total Pages Processed (Other): 3866
Total Pages Processed (Seg) : 0
Total Pages Failing (Seg) : 0
Total Pages Empty : 0
Total Pages Marked Corrupt : 4
Total Pages Influx : 0
Highest block SCN : 0 (0.0)

10g以後rman備份發現的壞塊資訊可以在v$database_block_corruption查到。

SQL> select * from v$database_block_corruption;

FILE# BLOCK# BLOCKS CORRUPTION_CHANGE# CORRUPTION_TYPE
---------- ---------- ---------- ------------------ ---------------
2 1217134 1 0 FRACTURED
508 2386314 1 0 FRACTURED
517 1115970 1 0 FRACTURED
2 1200166 1 0 FRACTURED
51 401698 1 0 FRACTURED
61 306642 1 0 FRACTURED
2 502554 1 0 FRACTURED
2 1213658 1 0 FRACTURED
34 701050 1 0 FRACTURED
60 347166 1 0 FRACTURED

FRACTURED意味著資料塊是物理損壞，遇到這種情況，如果有備份的話最好是從備份恢復，甚至可以用rman做塊級恢復，如
blockrecover datafile 2 block 1217134;
或者：
blockrecover corruption list;

不幸的是，這個資料庫是一個新庫，沒有正式上線，也還沒有上備份。沒辦法，只能看看損壞的物件是什麼了。

--由於庫太大，直接查dba_extents太慢，因此備份dba_extents到表dbextnet再查詢。

SQL> select * from dbextent where file_id=2 and 1213658 between block_id and block_id+blocks-1;

OWNER SEGMENT_NAME PARTITION_NAME SEGMENT_TYPE TABLESPACE_NAME EXTENT_ID FILE_ID BLOCK_ID BYTES BLOCKS RELATIVE_FNO
------------------------------ -------------------------------------------------------------------------------- ------------------------------ ------------------ ------------------------------ ---------- ---------- ---------- ---------- ---------- ------------
CREATER_USER WIDGET_NEWUSE_IX2 INDEX DWDATA_1M 995 2 1213637 1048576 64 2

SQL> select * from dbextent where file_id=2 and 502554 between block_id and block_id+blocks-1;

OWNER SEGMENT_NAME PARTITION_NAME SEGMENT_TYPE TABLESPACE_NAME EXTENT_ID FILE_ID BLOCK_ID BYTES BLOCKS RELATIVE_FNO
------------------------------ -------------------------------------------------------------------------------- ------------------------------ ------------------ ------------------------------ ---------- ---------- ---------- ---------- ---------- ------------
CREATER_USER WIDGET_NEWUSE_IX2 INDEX DWDATA_1M 1787 2 502533 1048576 64 2

萬幸的是，這裡損壞的只是索引，把索引rebuild就可以。如果損壞的是表，則可能需要用到其他手段，如dbms_repare包來處理了。

SQL> alter index creater_user.WIDGET_NEWUSE_IX2 rebuild online parallel 16 tablespace dwdata_10m_1 nologging;

Index altered

......

注意：這裡要用rebuild online，否則rebuild可能會讀取原索引作為源來重建新索引，這樣的話新建的索引也是損壞的。

全部處理完畢後，確認是否還有物件損壞。

SQL> select * from dba_extents E,v$database_block_corruption c where e.file_id=c.file# and c.block# between e.block_id and e.block_id+e.blocks-1;

OWNER SEGMENT_NAME PARTITION_NAME SEGMENT_TYPE TABLESPACE_NAME EXTENT_ID FILE_ID BLOCK_ID BYTES BLOCKS RELATIVE_FNO FILE# BLOCK# BLOCKS CORRUPTION_CHANGE# CORRUPTION_TYPE
------------------------------ -------------------------------------------------------------------------------- ------------------------------ ------------------ ------------------------------ ---------- ---------- ---------- ---------- ---------- ------------ ---------- ---------- ---------- ------------------ ---------------

以上查詢返回結果為空，表示沒有資料庫物件損壞，第一階段處理完畢。

一次壞塊的處理過程(一)

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