1.通过immediate trace name方式(在数据库open状态下)alter session set events
测试下_disable_logging将对数据库产生的影响，由于是隐含参数，所以我们通过如下方法获取对这个参数的描述：
sql> select ksppinm,ksppdesc from x$ksppi where ksppinm like '%logging';
ksppinm              ksppdesc
------------------------------------
_disable_logging     disable logging
将其改为ture，也就是启用了不记录日志的方式：
sql> alter system set _disable_logging=true scope=both;
system altered.
创建一个，并模拟事务运行，生成大量的redo,
sql> create table mm tablespace marvener as select * from dba_objects;
table created.
sql> insert into mm  select * from dba_objects;
45167 rows created.
sql> /
45167 rows created.
这个时候突然掉电了，也就是shutdown abort关闭数据库：
sql> shutdown abort
oracle instance shut down.
sql> startup
oracle instance started.
total system global area 1610612736 bytes
fixed size                  2084296 bytes
variable size             385876536 bytes
database buffers         1207959552 bytes
redo buffers               14692352 bytes
database mounted.
ora-00354: corrupt redo log block header
ora-00353: log corruption near block 81435 change 856029 time 01/30/2012
15:50:39
ora-00312: online log 1 thread 1: '/u01/app/oracle/oradata/marven/redo01.log'
如上。可以发现数据库无法正常打开，并提示重做日志块头损坏，在告警中可见大量的如下告警信息：
试图通过resetlogs方式打开数据库：
alter system set _allow_resetlogs_corruption=true scope=spfile;
shutdown abort
startup
数据库仍然会显然如下告警，，并强制关闭实例：
smon: enabling cache recovery
mon jan 30 16:15:41 2012
errors in file /u01/app/oracle/admin/marven/udump/marven_ora_2900.trc:
ora-00600: internal error code, arguments: [2662], [0], [855728], [0], [855937], [8388649], [], []
mon jan 30 16:15:42 2012
errors in file /u01/app/oracle/admin/marven/udump/marven_ora_2900.trc:
ora-00600: internal error code, arguments: [2662], [0], [855728], [0], [855937], [8388649], [], []
mon jan 30 16:15:42 2012
error 600 happened during db open, shutting down database
user: terminating instance due to error 600
instance terminated by user, pid = 2900
ora-1092 signalled during: alter database open resetlogs...
mon jan 30 16:16:34 2012
此时我们可以通过oracle的内部事件来调整scn:
增进scn有两种常用方法:
1.通过immediate trace name方式(在数据库open状态下)
alter session set events 'immediate trace name adjust_scn level x';
2.通过10015事件(在数据库无法打开，mount状态下)
alter session set events '10015 trace name adjust_scn level x';
注:level 1为增进scn 10亿 (1 billion) (1024*1024*1024),通常level 1已经足够。也可以根据实际情况适当调整。
本次由于数据库并未打开，而处于mount状态，所以只能通过第二种方式：
alter session set events '10015 trace name adjust_scn level 10';
sql> alter database open;
database altered.