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Oracle数据恢复:ORA-00600 6749与ORA-8102

最近,在帮助用户进行数据恢复之后遇到了一个ORA-00600 6749问题,这个错误实际上有多种可能,在这个客户系统中,也并不是因为恢复问题导致的,只是这个问题以前并没有被注意到。

多年以前,在ITPUB上就曾经探讨过这个问题, Oracle有一个BUG,在某行记录上,会将ROWID指向自身,这样当读取到这条记录时就可能产生死循环,无法跳出这条记录。

这在MOS被标记为BUG:7705591 :
Bug 7705591  Corruption with self-referenced row in MSSM tablespace. Wrong Results / OERI[6749] / ORA-8102

A chained row (logical row continued in another row) in a table
can be corrupted where the next row piece (nrid) points to itself.

Data corruption resulting from a lost row piece can occur very
intermittently in blocks experiencing high concurrency in MSSM
tablespaces (dba_tablespaces.segment_space_management=MANUAL).

It is most likely to happen but not limited to tables with a large
number of columns (e.g. more than 255 columns).
Subsequent SQL operations may produce wrong results or different
errors like:

ORA-600 [6749] by DELETE
ORA-8102 by UPDATE (if the table has indexes)
ORA-600 [qertbFetchByRowID]
ORA-1499 by "analyze table <name> validate structure cascade"
        (logical corruption between index and table
         as the table is returning wrong values for the affected
Without the fix of Bug 8720802 tools like DBVERIFY / RMAN / ANALYZE
don't detect this logical corruption.

Corruption Example from a block dump:

Row 3 in Block rdba 0xad858746 :  << BLOCK 的地址信息

tab 0, row 3, @0x6e9
tl: 127 fb: --H-F--- lb: 0x0  cc: 33
nrid:  0xad858746.3  --> it points to the same row 3
<< 这里的NRID 指 Next ROWID,行链接行的下一个块地址,这里的NRID指向了自身,读取会出现循环,无法跳出。

The fix for this bug does not repair existent corruptions.


update db_testresultinfo_old set f_depreagentoutlay = 0, f_depamtreagentoutlay = 0
where  f_inputdate2 between to_date('2010-03-01 00:00:01', 'yyyy-mm-dd hh24:mi:ss') and
    to_date('2010-03-31 23:59:59', 'yyyy-mm-dd hh24:mi:ss')
ORA-00600: 内部错误代码, 参数: [6749], [3], [18051454], [18], [], [], [], []
execute dbms_stats.delete_schema_stats('ZJLM_USER');
ZJLM_USER 是你报错的那个表所属的oracle用户
我没有敢做SCHEMA的删除,重新搜集了下该表的统计信息 ,再次更新时就成功了。以下是执行步骤:
SQL> exec dbms_stats.gather_table_stats(ownname => 'KMS',tabname=>'DB_TESTRESULTINFO_OLD');
PL/SQL procedure successfully completed
SQL> update db_testresultinfo_old 
                 set   f_depreagentoutlay = 0,
                          f_depamtreagentoutlay = 0
                 where  f_inputdate2
                     between  to_date('2010-03-01 00:00:01', 'yyyy-mm-dd hh24:mi:ss') 
                     and   to_date('2010-03-01 13:59:59', 'yyyy-mm-dd hh24:mi:ss')
2287 rows updated
这个案例与统计信息有关,注意 6749 的参数 18051454 是数据块的DBA,通过这个数字转换,应该可以找到相应的数据块。这个案例很有意思,转引供参考。

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By eygle on 2012-03-12 08:28 | Comments (0) | Backup&Recovery | 2967 |

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