一、问题描述
1、数据库情况
1）数据库版本：11.2.0.4
2）未开启归档
3）没有备份：无RMAN备份、无DUMP备份
2、问题出现原因
因公司断电，导致生产数据库宕机，开启后，出现ORA-00600[2662]问题。
通过查看数据库状态，只能开启到mount状态，并且有一个日志文件损坏，而且损坏的是current redo log。
ORA-00600[2662]原因如下：
1）A data block SCN is ahead of the current SCN.(SCN不一致)
2）Bug 14351566 ORA-600 [kclchkblk_4] ORA-600 [2662] when doing flash back；
二、问题处理思路
排除了因为Bug导致ORA-00600[2662]的错误，那么错误就定位在SCN不一致上面。
因为没有可用的日志、备份、归档等条件，只能采用重建控制文件，并通过设置Oracle内部隐含参数_allow_resetlogs_corruption=TRUE跳过一致性检查，强制open数据库。
三、解决步骤
1、参数文件中加入_allow_resetlogs_corruption=TRUE
alter system set _allow_resetlogs_corruption=TRUE scope=spfile;
2、重建控制文件
CREATE CONTROLFILE REUSE DATABASE "TRSDB" RESETLOGS NOARCHIVELOG --注意：因为数据库本身就是非归档模式，所以也以非归档模式重建
-- SET STANDBY TO MAXIMIZE PERFORMANCE
MAXLOGFILES 5
MAXLOGMEMBERS 3
MAXDATAFILES 100
MAXINSTANCES 1
MAXLOGHISTORY 226
LOGFILE
GROUP 1 '/home/oracle/app/oracle/oradata/trsdb/redo01.log' SIZE 50M,
GROUP 2 '/home/oracle/app/oracle/oradata/trsdb/redo02.log' SIZE 50M,
GROUP 3 '/home/oracle/app/oracle/oradata/trsdb/redo03.log' SIZE 50M
-- STANDBY LOGFILE
DATAFILE
'/home/oracle/app/oracle/oradata/trsdb/system01.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sysaux01.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb12_2.dbf',
'/home/oracle/app/oracle/oradata/trsdb/users01.dbf',
'/home/oracle/app/oracle/oradata/trsdb/bigdb.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb01.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb02.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb03.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb04.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb05.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb06.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb07.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb08.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb09.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb10.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb11.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb12.dbf',
'/home/oracle/app/oracle/oradata/trsdb/device01.dbf',
'/home/oracle/app/oracle/oradata/trsdb/device02.dbf',
'/home/oracle/app/oracle/oradata/trsdb/device03.dbf',
'/home/oracle/app/oracle/oradata/trsdb/device04.dbf',
'/home/oracle/app/oracle/oradata/trsdb/device05.dbf',
'/home/oracle/app/oracle/oradata/trsdb/device06.dbf',
'/home/oracle/app/oracle/oradata/trsdb/device07.dbf',
'/home/oracle/app/oracle/oradata/trsdb/device08.dbf',
'/home/oracle/app/oracle/oradata/trsdb/device09.dbf',
'/home/oracle/app/oracle/oradata/trsdb/device10.dbf',
'/home/oracle/app/oracle/oradata/trsdb/device11.dbf',
'/home/oracle/app/oracle/oradata/trsdb/device12.dbf',
'/home/oracle/app/oracle/oradata/trsdb/bigdb-01.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb08-01.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb09-01.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb10-1.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb07-01.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb06-01.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb05-01.dbf',
'/home/oracle/app/oracle/oradata/trsdb/device11_2.dbf',
'/home/oracle/app/oracle/oradata/trsdb/device11_3.dbf',
'/home/oracle/app/oracle/oradata/trsdb/device11_4.dbf',
'/home/oracle/app/oracle/oradata/trsdb/device11_5.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb12_1.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb01a.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb01b.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb021.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb02-01.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb07-02.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb10-02.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb03-02.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb06-02.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb11-02.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb09-02.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb04-03.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb05-02.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb02-02.dbf',
'/home/oracle/app/oracle/oradata/trsdb/bigdb-02.dbf',
'/home/oracle/app/oracle/oradata/trsdb/bigdb-03.dbf',
'/home/oracle/app/oracle/oradata/trsdb/bigdb-04.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb01c.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb03-01.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb04-02.dbf',
'/home/oracle/app/oracle/product/11.2.0/dbhome_1/dbs/SGDB07_2018060817_1.dbf',
'/home/oracle/app/oracle/product/11.2.0/dbhome_1/dbs/SGDB08_2018061109_2.dbf',
'/home/oracle/app/oracle/product/11.2.0/dbhome_1/dbs/SGDB09_2018061917_1.dbf',
'/home/oracle/app/oracle/product/11.2.0/dbhome_1/dbs/SGDB10_2018062618_3.dbf',
'/home/oracle/app/oracle/product/11.2.0/dbhome_1/dbs/SGDB12_2018071420_1.dbf',
'/home/oracle/app/oracle/product/11.2.0/dbhome_1/dbs/SGDB02_2018072309_1.dbf',
'/home/oracle/app/oracle/product/11.2.0/dbhome_1/dbs/SGDB01_2018072409_1.dbf',
'/home/oracle/app/oracle/product/11.2.0/dbhome_1/dbs/SGDB01_2018072409_2.dbf',
'/home/oracle/app/oracle/product/11.2.0/dbhome_1/dbs/DEVICE01_2018072409_1.dbf',
'/home/oracle/app/oracle/product/11.2.0/dbhome_1/dbs/DEVICE02_2018072409_1.dbf',
'/home/oracle/app/oracle/product/11.2.0/dbhome_1/dbs/DEVICE03_2018072717_1.dbf',
'/home/oracle/app/oracle/product/11.2.0/dbhome_1/dbs/SGDB06_2018072717_1.dbf',
'/home/oracle/app/oracle/product/11.2.0/dbhome_1/dbs/DEVICE08_2018072717_2.dbf',
'/home/oracle/app/oracle/product/11.2.0/dbhome_1/dbs/DEVICE09_2018072717_2.dbf',
'/home/oracle/app/oracle/product/11.2.0/dbhome_1/dbs/SGDB05_2018072717_2.dbf',
'/home/oracle/app/oracle/product/11.2.0/dbhome_1/dbs/SGDB03_2018072718_1.dbf',
'/home/oracle/app/oracle/product/11.2.0/dbhome_1/dbs/DEVICE06_2018072718_2.dbf',
'/home/oracle/app/oracle/product/11.2.0/dbhome_1/dbs/DEVICE07_2018072718_2.dbf',
'/home/oracle/app/oracle/oradata/trsdb/device04-01.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb04-01.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb09-03.dbf',
'/home/oracle/app/oracle/oradata/trsdb/sgdb08-02.dbf',
'/home/oracle/app/oracle/oradata/trsdb/audit01.dbf',
'/home/oracle/app/oracle/oradata/trsdb/undotbs02.dbf'
;
3、恢复数据库
1）recover database using backup controlfile until cancel;
2）alter database open resetlogs;
开启后还会有ORA-600 [2662]，这是就需要手动改变Oracle整个数据库的SCN，是的数据文件、控制文件等SCN统一。
4、使用oradebug poke推进SCN
1）oradebug setmypid
2）oradebug dumpvar sga kcsgscn_
3）oradebug poke 0x060012658 8 10014077592
4）oradebug dumpvar sga kcsgscn_
5）alter database open;
至此数据库恢复完毕，后面还需要将数据导出，并重建这个非常规恢复的数据库。
四、事后总结
1、在做这次数据库恢复时，从网上选取了多种恢复方法，最后得到只有oradebug poke推进SCN的方法适合11.2.0.4版本，其他方法已经不适用；
2、数据库处于整个系统的终端，对数据库做的各种安全保护手段都不为过
1）必须对数据库做定期备份（RMAN/DUMP）
2）必须对日志文件使用日志组的方式，这样可以保证，同一组内的一个redo log损坏，可以有后备的redo log继续工作；
3）必须开启归档日志。