有时候数据库挂掉，起库会出现ORA-00704错误，而导致ORA-00704错误的根本原因是访问OBJ$的时候，ORACLE需要回滚段中的数据，而访问回滚段的时候需要的undo数据已经被覆盖，此时我们可以通过bbed工具手工提交事务，从而解决这个问题。
使用bbed提交事务测试过程如下：
JP@ORCL>create table JP_BBED_TEST as select * from hr.employees where rownum<=10;
Table created.
JP@ORCL>select rowid, dbms_rowid.rowid_relative_fno(rowid)rel_fno,
dbms_rowid.rowid_block_number(rowid)blockno,
dbms_rowid.rowid_row_number(rowid) rowno
from jp_bbed_test; 2 3 4
ROWID REL_FNO BLOCKNO ROWNO
------------------ ---------- ---------- ----------
AAAM7wAAEAAAAGcAAA 4 412 0
AAAM7wAAEAAAAGcAAB 4 412 1
AAAM7wAAEAAAAGcAAC 4 412 2
AAAM7wAAEAAAAGcAAD 4 412 3
AAAM7wAAEAAAAGcAAE 4 412 4
AAAM7wAAEAAAAGcAAF 4 412 5
AAAM7wAAEAAAAGcAAG 4 412 6
AAAM7wAAEAAAAGcAAH 4 412 7
AAAM7wAAEAAAAGcAAI 4 412 8
AAAM7wAAEAAAAGcAAJ 4 412 9
10 rows selected.
JP@ORCL>select last_name from jp_bbed_test;
LAST_NAME
-------------------------
OConnell
Grant
Whalen
Hartstein
Fay
Mavris
Baer
Higgins
Gietz
King
10 rows selected.
JP@ORCL>update jp_bbed_test set LAST_NAME='BADLY9';
10 rows updated.
此时事务没有提交，其他的session是无法查看此时的修改的。
另开一个窗口
[oracle@jp bbed]$ sqlplus / as sysdba
SQL*Plus: Release 10.2.0.1.0 - Production on Fri Jun 6 06:56:52 2014
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
SYS@ORCL>alter system checkpoint;
System altered.
SYS@ORCL>alter system dump datafile 4 block 412;
System altered.
SYS@ORCL>oradebug setmypid
Statement processed.
SYS@ORCL>oradebug tracefile_name
/u01/app/oracle/admin/ORCL/udump/orcl_ora_17715.trc
查看/u01/app/oracle/admin/ORCL/udump/orcl_ora_17715.trc文件
我们可以看到以下内容：
Block header dump: 0x0100019c
Object id on Block Y
seg/obj: 0xcef0 csc: 0x00.c3cf8 itc: 3 flg: E typ: 1 - DATA
brn: 0 bdba: 0x1000199 ver: 0x01 opc: 0
inc: 0 exflg: 0
Itl Xid Uba Flag Lck Scn/Fsc
0x01 0xffff.000.00000000 0x00000000.0000.00 C--- 0 scn 0x0000.000c3cf8
0x02 0x0006.02b.000001a1 0x008000d0.00f6.2a ---- 10 fsc 0x0000.00000000
0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000
这里可以看到我们LCK了10条表中记录
这时候我们使用bbed将事务提交：
首先使用session2 flush buffer_pool，如果不清空buffer pool，再次读取该block时将不会进行物理读，无法看到修改后的结果而且会覆盖我们的修改：
SYS@ORCL>alter system flush buffer_cache;
System altered.
使用bbed工具进行修改：
BBED> set dba 4,412
DBA 0x0100019c (16777628 4,412)
BBED> map
File: /u01/app/oracle/oradata/ORCL/users01.dbf (4)
Block: 412 Dba:0x0100019c
------------------------------------------------------------
KTB Data Block (Table/Cluster)
struct kcbh, 20 bytes @0
struct ktbbh, 96 bytes @20
struct kdbh, 14 bytes @124
struct kdbt[1], 4 bytes @138
sb2 kdbr[10] @142
ub1 freespace[6794] @162
ub1 rowdata[1232] @6956
ub4 tailchk @8188
BBED> p ktbbh
struct ktbbh, 96 bytes @20
ub1 ktbbhtyp @20 0x01 (KDDBTDATA)
union ktbbhsid, 4 bytes @24
ub4 ktbbhsg1 @24 0x0000cef0
ub4 ktbbhod1 @24 0x0000cef0
struct ktbbhcsc, 8 bytes @28
ub4 kscnbas @28 0x000c3cf8
ub2 kscnwrp @32 0x0000
b2 ktbbhict @36 3
ub1 ktbbhflg @38 0x32 (NONE)
ub1 ktbbhfsl @39 0x00
ub4 ktbbhfnx @40 0x01000199
struct ktbbhitl[0], 24 bytes @44
struct ktbitxid, 8 bytes @44
ub2 kxidusn @44 0xffff
ub2 kxidslt @46 0x0000
ub4 kxidsqn @48 0x00000000
struct ktbituba, 8 bytes @52
ub4 kubadba @52 0x00000000
ub2 kubaseq @56 0x0000
ub1 kubarec @58 0x00
ub2 ktbi