http://www.ixdba.net/article/f9/277.html
现场情况：
    1、数据库没有作归档，
    2、数据都存放在system表空间
    3、没有备份
状况：
    操作系统由于磁盘原因出现宕机，用户强行按电源关闭系统，数据库无法启动。
处理：

SQL> recover database;
ORA-00283: recovery session canceled due to errors
ORA-12801: error signaled in parallel query server P002
ORA-10562: Error occurred while applying redo to data block (file# 1, block#4568)
ORA-10564: tablespace SYSTEM
ORA-01110: data file 1: '/opt/oracle/oradata/orcl/system01.dbf'
ORA-10561: block type 'TRANSACTION MANAGED INDEX BLOCK', data object# 576
ORA-00600: internal error code, arguments: [6101]

检查日志信息如下：

Mon Nov 19 15:38:50 2007
ALTER DATABASE RECOVER  database
Mon Nov 19 15:38:50 2007
Media Recovery Start
parallel recovery started with 3 processes
Mon Nov 19 15:38:50 2007
Recovery of Online Redo Log: Thread 1 Group 3 Seq 16 Reading mem 0
Mem# 0 errs 0: /opt/oracle/oradata/orcl/redo03.log
Mon Nov 19 15:38:50 2007
Errors in file /opt/oracle/admin/orcl/bdump/orcl_p002_7917.trc:
ORA-00600: internal error code, arguments: [6101], [0], [17], [0], [], [], [], []
Mon Nov 19 15:38:50 2007
Errors in file /opt/oracle/admin/orcl/bdump/orcl_p000_7913.trc:
ORA-00600: internal error code, arguments: [3020], [2], [882], [8389490], [], [], [], []
ORA-10567: Redo is inconsistent with data block (file# 2, block# 882)
ORA-10564: tablespace UNDOTBS1
ORA-01110: data file 2: '/opt/oracle/oradata/orcl/undotbs01.dbf'
ORA-10560: block type 'KTU UNDO BLOCK'
Mon Nov 19 15:38:51 2007
Errors in file /opt/oracle/admin/orcl/bdump/orcl_p000_7913.trc:
ORA-00600: internal error code, arguments: [3020], [2], [882], [8389490], [], [], [], []
ORA-10567: Redo is inconsistent with data block (file# 2, block# 882)
ORA-10564: tablespace UNDOTBS1
ORA-01110: data file 2: '/opt/oracle/oradata/orcl/undotbs01.dbf'
ORA-10560: block type 'KTU UNDO BLOCK'
Mon Nov 19 15:38:51 2007
Errors in file /opt/oracle/admin/orcl/bdump/orcl_p002_7917.trc:
ORA-10562: Error occurred while applying redo to data block (file# 1, block# 4568)
ORA-10564: tablespace SYSTEM
ORA-01110: data file 1: '/opt/oracle/oradata/orcl/system01.dbf'
ORA-10561: block type 'TRANSACTION MANAGED INDEX BLOCK', data object# 576
ORA-00600: internal error code, arguments: [6101], [0], [17], [0], [], [], [], []
Mon Nov 19 15:38:54 2007
Errors in file /opt/oracle/admin/orcl/bdump/orcl_p001_7915.trc:
ORA-00600: internal error code, arguments: [kddummy_blkchk], [1], [1658], [6101], [], [], [], []
Mon Nov 19 15:38:54 2007
Errors in file /opt/oracle/admin/orcl/bdump/orcl_p001_7915.trc:
ORA-10562: Error occurred while applying redo to data block (file# 1, block# 1658)
ORA-10564: tablespace SYSTEM
ORA-01110: data file 1: '/opt/oracle/oradata/orcl/system01.dbf'
ORA-10561: block type 'TRANSACTION MANAGED DATA BLOCK', data object# 237
ORA-00607: Internal error occurred while making a change to a data block
ORA-00600: internal error code, arguments: [kddummy_blkchk], [1], [1658], [6101], [], [], [], []
Mon Nov 19 15:38:54 2007
Media Recovery failed with error 12801
ORA-283 signalled during: ALTER DATABASE RECOVER  database  ...

从上面信息中抓取了一个信息：

ORA-10562: Error occurred while applying redo to data block (file# 1, block# 1658)

针对这个错误解决如下：

ORA-10562: Error occurred while applying redo to data block (file# string, block# string)
Cause: See other errors on error stack.
Action: Investigate why the error occurred and how important is the data block. Media and standby database recovery usually can continue if user allows recovery to corrupt this data block。

从日志信息可以基本判断问题如下：
当前在线日志损坏，导致undo回滚段出现问题，又由于系统突然掉电，系统表空间在重启实例后要进行实例恢复，当前在线日志损坏，系统表空间无法进行recover，因而出现了上面的错误。
找到了问题，解决访问就有了。
由于没有备份，数据库也运行在非归档模式下，所以恢复如下步骤：

SQL>startup mount
SQL>recover database using backup controlfile until cancel;
SQL>alter database open resetlogs;
SQL> startup mount
SQL> alter system set “_allow_resetlogs_corruption”=true scope=spfile;
SQL>shutdown immediate
SQL> startup mount
SQL> alter database open resetlogs;
SQL> startup

基本恢复步骤：

SQL>startup mount
SQL>recover database using backup controlfile until cancel;
Cancel
SQL>alter database open resetlogs;
#此时会提示system表空间需要恢复，但是由于当前日志损坏，无法进行恢复，所以需要加入#隐含参数，oracle才不会监测scn的一致性，才能打开数据库。
#重启数据库加入隐含参数
SQL> startup mount
SQL> alter system set “_allow_resetlogs_corruption”=true scope=spfile;
SQL> shutdown immediate
SQL> startup mount
SQL> alter database open resetlogs;
alter database open resetlogs
*
ERROR at line 1:
ORA-01092: ORACLE instance terminated. Disconnection forced
#不管这些，再次登录sqlplus起动数据库
SQL*Plus: Release 10.2.0.1.0 - Production on Fri Nov 16 08:03:43 2007
Copyright (c) 1982, 2005, Oracle.  All rights reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options
SQL>startup

数据库正常打开，exp备份需要的数据，然后重新建库，导入数据。
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    通过这次操作，我得到一个经验，在处理Oracle问题时，切忌慌乱，对于出现的问题，通过看Oracle的alert.log以及trace文件，分析出现问题的错误，逐步定位，然后就是在网上搜索或者请教高人。