ORA-08103错误情景再现及解决

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$ oerr ora 8103
08103, 00000, “object no longer exists”
// *Cause: The object has been deleted by another user since the operation
// began, or a prior incomplete recovery restored the database to
// a point in time during the deletion of the object.
// *Action: Delete the object if this is the result of an incomplete
// recovery.

在 Master Note for Handling Oracle Database Corruption Issues (文档 ID 1088018.1) 中对 ORA-8103 错误的描述如下：

The object has been deleted by another user since the operation began.
If the error is reproducible, following may be the reasons:-
a.) The header block has an invalid block type.
b.) The data_object_id (seg/obj) stored in the block is different than the data_object_id stored in the segment header.

See dba_objects.data_object_id and compare it to the decimal value stored in the block (field seg/obj).

–// 以前做过的测试. 链接:http://blog.itpub.net/267265/viewspace-2131848/
–// 听别人提起高水位下的块出现了未格式化的块. 自己模拟测试看看.

1. 环境:
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

–// 建立表空间:
CREATE TABLESPACE TEA DATAFILE
‘/mnt/ramdisk/book/tea01.dbf’ SIZE 40M AUTOEXTEND ON NEXT 1M MAXSIZE UNLIMITED
LOGGING
ONLINE
EXTENT MANAGEMENT LOCAL AUTOALLOCATE
BLOCKSIZE 8K
SEGMENT SPACE MANAGEMENT MANUAL
FLASHBACK ON;

–// 顺便做 1 个备份.
RMAN> backup as copy datafile 6 format ‘/home/oracle/backup/%b’ ;
Starting backup at 2018-11-22 16:22:12
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=67 device type=DISK
allocated channel: ORA_DISK_2
channel ORA_DISK_2: SID=94 device type=DISK
allocated channel: ORA_DISK_3
channel ORA_DISK_3: SID=106 device type=DISK
channel ORA_DISK_1: starting datafile copy
input datafile file number=00006 name=/mnt/ramdisk/book/tea01.dbf
output file name=/home/oracle/backup/tea01.dbf tag=TAG20181122T162213 RECID=13 STAMP=992881334
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:01
Finished backup at 2018-11-22 16:22:15

Starting Control File and SPFILE Autobackup at 2018-11-22 16:22:15
piece handle=/u01/app/oracle/fast_recovery_area/BOOK/autobackup/2018_11_22/o1_mf_s_992881335_fzdssq4g_.bkp comment=NONE
Finished Control File and SPFILE Autobackup at 2018-11-22 16:22:16

2. 建立测试环境:
SCOTT@book> create table t tablespace tea as select * from all_objects where rownum<=1e4;
Table created.

SCOTT@book> select object_id,data_object_id from dba_objects where object_name = ‘T’ and owner = user;
OBJECT_ID DATA_OBJECT_ID
———- ————–
90463 90463

SCOTT@book> select segment_type, HEADER_FILE, HEADER_BLOCK from dba_segments where owner = user and segment_name = ‘T’;
SEGMENT_TYPE HEADER_FILE HEADER_BLOCK
—————— ———– ————
TABLE 6 128

SCOTT@book> select FILE_ID, block_id, blocks from dba_extents where owner = user and segment_name = ‘T’;
FILE_ID BLOCK_ID BLOCKS
———- ———- ———-
6 128 8
6 136 8
6 144 8
6 152 8
6 160 8
6 168 8
6 176 8
6 184 8
6 192 8
6 200 8
6 208 8
6 216 8
6 224 8
6 232 8
6 240 8
6 248 8
6 256 128
17 rows selected.

2. 破坏数据块看看:
SCOTT@book> alter system flush buffer_cache;
System altered.

SCOTT@book> select max(rowid) from t ;
MAX(ROWID)
——————
AAAWFfAAGAAAAEBABJ

SCOTT@book> @ rowid AAAWFfAAGAAAAEBABJ
OBJECT FILE BLOCK ROW ROWID_DBA DBA TEXT
———- ———- ———- ———- ——————– ——————– —————————————-
90463 6 257 73 0x1800101 6,257 alter system dump datafile 6 block 257 ;

–//dba=6,257 块上有数据.

SCOTT@book> insert into t select * from all_objects where rownum<=1;
1 row created.

SCOTT@book> commit ;
Commit complete.

SCOTT@book> alter system flush buffer_cache;
System altered.

SCOTT@book> @ rowid AAAWFfAAGAAAAECAAA
OBJECT FILE BLOCK ROW ROWID_DBA DBA TEXT
———- ———- ———- ———- ——————– ——————– —————————————-
90463 6 258 0 0x1800102 6,258 alter system dump datafile 6 block 258 ;

–//dba=6,258 块上有数据. 通过 bbed 观察 dba=6,259
BBED> map dba 6,259
File: /mnt/ramdisk/book/tea01.dbf (6)
Block: 259 Dba:0x01800103
————————————————————
KTB Data Block (Table/Cluster)
struct kcbh, 20 bytes @0
struct ktbbh, 72 bytes @20
struct kdbh, 14 bytes @92
struct kdbt[0], 0 bytes @106
sb2 kdbr[0] @106
ub1 freespace[8082] @106
ub1 rowdata[0] @8188
ub4 tailchk @8188

–// 可以发现 dba=6,259 已经格式化. 但是没有数据.
SCOTT@book> select count(*) from t;
COUNT(*)
———-
10001
–//OK 一切正常. 现在破坏 dba=6,259

BBED> set offset 0
OFFSET 0
–// 注意一定要设置 offset 0, 不然可能 copy 仅仅剩下的部分.

BBED> copy filename ‘/home/oracle/backup/tea01.dbf’ block 259 to filename ‘/mnt/ramdisk/book/tea01.dbf’ block 259
Warning: contents of previous BIFILE will be lost. Proceed? (Y/N) y
File: /mnt/ramdisk/book/tea01.dbf (6)
Block: 259 Offsets: 0 to 63 Dba:0x01800103
————————————————————————————————————————————————
00a20000 03018001 00000000 00000105 83a70000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
<64 bytes per line>

–// 现在已经未格式化块.

4. 继续测试:
SCOTT@book> alter system flush buffer_cache;
System altered.

SCOTT@book> select count(*) from t;
select count(*) from t
*
ERROR at line 1:
ORA-08103: object no longer exists
–// 再线 ora-08103.
–// 而执行如下不会报错:
SCOTT@book> select count(*) from t where rownum<=10001;
COUNT(*)
———-
10001
SCOTT@book> select count(*) from t where rownum<=10002;
select count(*) from t where rownum<=10002
*
ERROR at line 1:
ORA-08103: object no longer exists

–// 检查跟踪文件:
kcbzibmlt: dump suspect buffer, err=8103
buffer tsn: 7 rdba: 0x01800103 (6/259)
scn: 0x0000.00000000 seq: 0x01 flg: 0x05 tail: 0x00000001
frmt: 0x02 chkval: 0xa783 type: 0x00=unknown
Hex dump of corrupt header 4 = CORRUPT
Dump of memory from 0x000000006A4EA000 to 0x000000006A4EA014
06A4EA000 0000A200 01800103 00000000 05010000 […………….]
06A4EA010 0000A783 [….]
Hex dump of block: st=4, typ_found=0
Dump of memory from 0x000000006A4EA000 to 0x000000006A4EC000
06A4EA000 0000A200 01800103 00000000 05010000 […………….]
06A4EA010 0000A783 00000000 00000000 00000000 […………….]
06A4EA020 00000000 00000000 00000000 00000000 […………….]
Repeat 508 times
06A4EBFF0 00000000 00000000 00000000 00000001 […………….]
Dump of buffer cache at level 8 for tsn=7 rdba=25166080

–// 可以发现 dba =6,259 报错.

5. 如何跳过呢?
–// 我测试仅仅设置坏块. 如果真有数据可以通过一些特殊的方式读出来, 这个给看运气. 通过 10231 事件跳过坏块

$ oerr ora 10231
10231, 00000, “skip corrupted blocks on _table_scans_”
// *Cause:
// *Action: such blocks are skipped in table scans, and listed in trace files
–//alter session set db_file_multiblock_read_count=1 ;
ALTER SESSION SET EVENTS ‘10231 TRACE NAME CONTEXT FOREVER, LEVEL 10’;

SCOTT@book> ALTER SESSION SET EVENTS ‘10231 TRACE NAME CONTEXT FOREVER, LEVEL 10’;
Session altered.

SCOTT@book> select count(*) from t ;
select count(*) from t
*
ERROR at line 1:
ORA-08103: object no longer exists

–// 不行. 在 bbed 设置坏块看看.
BBED> set dba 6,259
DBA 0x01800103 (25166083 6,259)

BBED> corrupt
Block marked media corrupt.

BBED> sum apply ;
Check value for File 6, Block 259:
current = 0xa683, required = 0xa683

SCOTT@book> select count(*) from t ;
COUNT(*)
———-
10001

–//ok. 跳过坏块.

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