Oracle数据库恢复：归档日志损坏案例一则

链接：http://www.eygle.com/archives/2010/11/recover_archivelog_corruption.html

最近在紧急故障处理时，帮助用户恢复数据库遇到了一则罕见的归档日志损坏案例，在这里和大家分享一下，看看是否有人遇到过类似的问题。

在进行归档recover时，数据库报错，提示归档日志损坏：

***
Corrupt block seq: 37288 blocknum=1.
Bad header found during deleting archived log
Data in bad block - seq:810559520. bno:170473264. time:707406346
beg:21280 cks:21061
calculated check value: 9226
Reread of seq=37288, blocknum=1, file=/ARCH/arch_1_37288_632509987.dbf, found same corrupt data
Reread of seq=37288, blocknum=1, file=/ARCH/arch_1_37288_632509987.dbf, found same corrupt data
Reread of seq=37288, blocknum=1, file=/ARCH/arch_1_37288_632509987.dbf, found same corrupt data
Reread of seq=37288, blocknum=1, file=/ARCH/arch_1_37288_632509987.dbf, found same corrupt data
Reread of seq=37288, blocknum=1, file=/ARCH/arch_1_37288_632509987.dbf, found same corrupt data
***

信息比较详细，说37288号归档日志Header损坏，无法读取数据。

提一个小问题：如果你遇到了这样的错误？会怎样思考？

如果这个归档日志损坏了，其实我们仍然有办法跳过去，继续尝试恢复其他日志，但是客户数据重要，不能容忍不一致性，这时候就只能放弃部分数据，由前台重新提交数据了。这在业务上可以实现，也就不是大问题了。

好了，问题是为什么日志会损坏？是如何损坏的？

我首先要做的就是，看看日志文件的内容，通过最简单的命令将日志文件中的内容输出出来：
strings arch_1_37288_632509987.dbf > log.txt

然后检查生成的这个日志文件，我们就发现了问题。
在这个归档日志文件中，被写入了大量的跟踪文件内容，其中开头部分就是一个跟踪文件的全部信息。

这是一种我从来没有遇到过的现象，也就是说，当操作系统在写出跟踪文件时，错误的覆盖掉了已经存在的归档文件，最后导致归档日志损坏，非常奇妙，从所未见。

最后我的判断是，这个故障应当是操作系统在写出时出现了问题，存在文件的空间仍然被认为是可写的，这样就导致了写冲突，出现这类问题，应当立即检查硬件，看看是否是硬件问题导致了如此严重的异常。

Dump file /ADMIN/bdump/erp_p007_19216.trc
Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - Production
With the Partitioning, OLAP and Data Mining options
ORACLE_HOME = /DBMS/erp/erpdb/10g
Linux
eygle.com
2.6.9-34.ELhugemem
#1 SMP Fri Feb 24 17:04:34 EST 2006
i686
Instance name: erp
Redo thread mounted by this instance: 1
Oracle process number: 22
Unix process pid: 19216, image: [e-mail] (P007)
*** SERVICE NAME:() 2010-11-10 10:37:26.247
*** SESSION ID:(2184.1) 2010-11-10 10:37:26.247
*** 2010-11-10 10:37:26.247
KCRP: blocks claimed = 61, eliminated = 0
----- Recovery Hash Table Statistics ---------
Hash table buckets = 32768
Longest hash chain = 1
Average hash chain = 61/61 = 1.0
Max compares per lookup = 0
Avg compares per lookup = 0/61 = 0.0
----------------------------------------------
----- Recovery Hash Table Statistics ---------
Hash table buckets = 32768
Longest hash chain = 1
Average hash chain = 61/61 = 1.0
Max compares per lookup = 1
Avg compares per lookup = 1426/1426 = 1.0
----------------------------------------------
\GPAYMENTdxn
AP_CHECKS
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Dump file /ADMIN/bdump/erp_p002_19206.trc
Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - Production
With the Partitioning, OLAP and Data Mining options
ORACLE_HOME = /DBMS/erp/erpdb/10g
Linux
eygle.com
2.6.9-34.ELhugemem
#1 SMP Fri Feb 24 17:04:34 EST 2006
i686
Instance name: erp
Redo thread mounted by this instance: 1
Oracle process number: 17
Unix process pid: 19206, image: [e-mail] (P002)
*** SERVICE NAME:() 2010-11-10 10:37:26.263
*** SESSION ID:(2187.1) 2010-11-10 10:37:26.263
*** 2010-11-10 10:37:26.263
KCRP: blocks claimed = 84, eliminated = 0
----- Recovery Hash Table Statistics ---------
Hash table buckets = 32768
Longest hash chain = 1
Average hash chain = 84/84 = 1.0
Max compares per lookup = 0
Avg compares per lookup = 0/84 = 0.0
----------------------------------------------
----- Recovery Hash Table Statistics ---------
Hash table buckets = 32768
Longest hash chain = 1
Average hash chain = 84/84 = 1.0
Max compares per lookup = 1
Avg compares per lookup = 880/880 = 1.0
----------------------------------------------
^A&A
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Dump file /ADMIN/bdump/erp_p001_19204.trc
Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - Production
With the Partitioning, OLAP and Data Mining options
ORACLE_HOME = /DBMS/erp/erpdb/10g
Linux
eygle.com
2.6.9-34.ELhugemem
#1 SMP Fri Feb 24 17:04:34 EST 2006
i686
Instance name: erp
Redo thread mounted by this instance: 1
Oracle process number: 16
Unix process pid: 19204, image: [e-mail] (P001)
*** SERVICE NAME:() 2010-11-10 10:37:26.372
*** SESSION ID:(2189.1) 2010-11-10 10:37:26.372
*** 2010-11-10 10:37:26.372
KCRP: blocks claimed = 132, eliminated = 0
----- Recovery Hash Table Statistics ---------
Hash table buckets = 32768
Longest hash chain = 1
Average hash chain = 132/132 = 1.0
Max compares per lookup = 0
Avg compares per lookup = 0/132 = 0.0
----------------------------------------------
----- Recovery Hash Table Statistics ---------
Hash table buckets = 32768
Longest hash chain = 1
Average hash chain = 132/132 = 1.0
Max compares per lookup = 1
Avg compares per lookup = 3219/3219 = 1.0
----------------------------------------------
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Dump file /ADMIN/bdump/erp_p000_19202.trc
Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - Production
With the Partitioning, OLAP and Data Mining options
ORACLE_HOME = /DBMS/erp/erpdb/10g
Linux
eygle.com
2.6.9-34.ELhugemem
#1 SMP Fri Feb 24 17:04:34 EST 2006
i686
Instance name: erp
Redo thread mounted by this instance: 1
Oracle process number: 15
Unix process pid: 19202, image: [e-mail] (P000)
*** SERVICE NAME:() 2010-11-10 10:37:26.386
*** SESSION ID:(2190.1) 2010-11-10 10:37:26.386
*** 2010-11-10 10:37:26.386
KCRP: blocks claimed = 181, eliminated = 0
----- Recovery Hash Table Statistics ---------
Hash table buckets = 32768
Longest hash chain = 1
Average hash chain = 181/181 = 1.0
Max compares per lookup = 0
Avg compares per lookup = 0/181 = 0.0
----------------------------------------------
----- Recovery Hash Table Statistics ---------
Hash table buckets = 32768
Longest hash chain = 1
Average hash chain = 181/181 = 1.0
Max compares per lookup = 1
Avg compares per lookup = 8629/8629 = 1.0
----------------------------------------------
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如此少见的案例，在此与大家分享。

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