启动数据库报错
SQL> startup
ORACLE instance started.

Total System Global Area  167772160 bytes
Fixed Size                  1260720 bytes
Variable Size             150995792 bytes
Database Buffers            8388608 bytes
Redo Buffers                7127040 bytes
Database mounted.
ORA-01092: ORACLE instance terminated. Disconnection forced

alert.log导错
Wed Aug 10 12:31:11 2011
Errors in file /u01/admin/xienfei/udump/xff_ora_8568.trc:
ORA-00600: internal error code, arguments: [ktbdchk1: bad dscn], [], [], [], [], [], [], []

xff_ora_8568.trc内容
[ktbdchk] -- readers_dsz -- bad dscn
scn: 0x0000.b1e60c00scn: 0x0000.0011fca1
*** 2011-08-10 12:31:11.998
ksedmp: internal or fatal error
ORA-00600: internal error code, arguments: [ktbdchk1: bad dscn], [], [], [], [], [], [], []
Current SQL statement for this session:
select ctime, mtime, stime from obj$ where obj# = :1
根据上面错误判断，错误的scn为b1e60c00，不是整个数据文件的scn错误
而应该是一个对象的scn错误，所以继续在xff_ora_8568.trc文件中查找b1e60c00
找到结果如下：
Block header dump:  0x0040007a
 Object id on Block? Y
 seg/obj: 0x12  csc: 0x00.b1e60c00  itc: 1  flg: -  typ: 1 - DATA
     fsl: 0  fnx: 0x0 ver: 0x01

 Itl           Xid                  Uba         Flag  Lck        Scn/Fsc
0x01   0x0008.02a.000001d9  0x00802341.01bb.04  ----    1  fsc 0x0000.0011ae7c

data_block_dump,data header at 0x20fd6044
===============
tsiz: 0x1fb8
hsiz: 0xea
pbl: 0x20fd6044
bdba: 0x0040007a
     76543210
flag=--------
ntab=1
nrow=108
frre=-1
fsbo=0xea
fseo=0x453
avsp=0x369
tosp=0x369
0xe:pti[0]      nrow=108        offs=0

根据这个提示，发现dba为：0040007a的对象异常，查找对应的file_id，block
SQL> SELECT DBMS_UTILITY.data_block_address_file (TO_NUMBER ('40007a', 'XXXXXXXX')) file_id,
  2          DBMS_UTILITY.data_block_address_block (TO_NUMBER ('40007a', 'XXXXXXXX')) block_id
  3    FROM DUAL;

   FILE_ID   BLOCK_ID
---------- ----------
         1        122

使用bbed查看file=1，block=122的scn情况
BBED> p ktbbh
struct ktbbh, 48 bytes                      @20      
   ub1 ktbbhtyp                             @20       0x01 (KDDBTDATA)
   union ktbbhsid, 4 bytes                  @24      
      ub4 ktbbhsg1                          @24       0x00000012
      ub4 ktbbhod1                          @24       0x00000012
   struct ktbbhcsc, 8 bytes                 @28      
      ub4 kscnbas                           @28       0xb1e60c00
      ub2 kscnwrp                           @32       0x0000
   b2 ktbbhict                              @36       1
   ub1 ktbbhflg                             @38       0x02 (NONE)
   ub1 ktbbhfsl                             @39       0x00
   ub4 ktbbhfnx                             @40       0x00000000
   struct ktbbhitl[0], 24 bytes             @44      
      struct ktbitxid, 8 bytes              @44      
         ub2 kxidusn                        @44       0x0008
         ub2 kxidslt                        @46       0x002a
         ub4 kxidsqn                        @48       0x000001d9
      struct ktbituba, 8 bytes              @52      
         ub4 kubadba                        @52       0x00802341
         ub2 kubaseq                        @56       0x01bb
         ub1 kubarec                        @58       0x04
      ub2 ktbitflg                          @60       0x0001 (NONE)
      union _ktbitun, 2 bytes               @62      
         b2 _ktbitfsc                       @62       0
         ub2 _ktbitwrp                      @62       0x0000
      ub4 ktbitbas                          @64       0x0011ae7c

果然发现scn为0xb1e60c00，现在把其修改为：0x00124ac6（注意规则，一般linux下都是倒序）
BBED> set offset 28
        OFFSET          28

BBED> m /x c64a1200
BBED-00209: invalid number (c64a1200)
小技巧，一次性修改报错，尝试一次修改一点

BBED> m /x c64a
 File: /u01/oradata/xienfei/system01.dbf (0)
 Block: 122              Offsets:   28 to   43           Dba:0x00000000
------------------------------------------------------------------------
 c64ae6b1 00000000 01000200 00000000 

 <32 bytes per line>

BBED> set offset +2
        OFFSET          30

BBED> m /x 1200
 File: /u01/oradata/xienfei/system01.dbf (0)
 Block: 122              Offsets:   30 to   45           Dba:0x00000000
------------------------------------------------------------------------
 12000000 00000100 02000000 00000800 

 <32 bytes per line>

BBED> set offset -2
        OFFSET          28

BBED> dump
 File: /u01/oradata/xienfei/system01.dbf (0)
 Block: 122              Offsets:   28 to   43           Dba:0x00000000
------------------------------------------------------------------------
 c64a1200 00000000 01000200 00000000 

 <32 bytes per line>

BBED> sum apply
Check value for File 0, Block 122:
current = 0x3a4e, required = 0x3a4e

SQL> startup
ORACLE instance started.

Total System Global Area  167772160 bytes
Fixed Size                  1260720 bytes
Variable Size             150995792 bytes
Database Buffers            8388608 bytes
Redo Buffers                7127040 bytes
Database mounted.
Database opened.