问：当数据库出现坏块，回滚段里的部分数据不能读取时，应该用什么方法解决。
答： 具体方法如下;
首先应当检查一下swappALRT.log文件，会发现以下错误：
Tue Sep 21 10:34:08 2004
Errors in file E:\oracle\admin\swapp\bdump\swappSMON.TRC:
ORA-01578: ORACLE data block corrupted (file # 2, block # 24497)
ORA-01110: data file 2: 'E:\ORACLE\ORADATA\SWAPP\RBS01.DBF'
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此种现象说明回滚段表空间数据文件出现了坏块。这时需要新建一个回滚段表空间，把以前坏了的回滚段表空间drop掉，在新的回滚段表空间上建回滚段，所要建的回滚段和以前的一摸一样，让以后产生的回滚数据都写到新建的回滚段上。
首先停掉listener,不允许有新的应用连到数据库上做操作，然后down掉数据库，为了清除掉已有的数据库会话连接资源:
$lsnrctl stop
LSNRCTL for Solaris: Version 8.1.7.3.0 - Production
on 21-SEP-2004 17:40:36
(c) Copyright 1998 Oracle Corporation.? All rights
reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(
HOST=ipasdb)(PORT=1521)))
The command completed successfully.
$sqlplus internal/oracle
SQL*Plus: Release 8.1.7.0.0 - Production on Tue
Sep 21 17:41:24 2004
(c) Copyright 2000 Oracle Corporation.?
All rights reserved.
Connected to:
Oracle8i Enterprise Edition Release 8.1.7.3.0 - 64bit
Production
With the Partitioning option
JServer Release 8.1.7.3.0 - 64bit Production
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
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SQL>startup restrict (以受限模式启动数据库，为了防止其他用户登陆进来做相关操作，这时候只允许管理员登陆）
查找回滚段对应的表空间:
SQL> select tablespace_name,status from dba_tablespaces;
TABLESPACE_NAME??????????????? STATUS
------------------------------ ---------
SYSTEM???????????????????????? ONLINE
TOOLS????????????????????????? ONLINE
RBS??????????????????????????? ONLINE
TEMP?????????????????????????? ONLINE
USERS????????????????????????? ONLINE
INDX?????????????????????????? ONLINE
DRSYS????????????????????????? ONLINE
WACOS????????????????????????? ONLINE
NMS??????????????????????????? ONLINE
TEST?????????????????????????? ONLINE
FS???????????????????????????? ONLINE
PERFSTAT?????????????????????? ONLINE
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12rows selected.
回滚段表空间为RBS.
查看当前回滚段表空间里是否有活动的事物:
SQL> SELECT s.username,t.xidusn,t.ubafil,
t.ubablk,t.used_ublk? FROM
v$session s,v$transaction t WHERE s.saddr=t.ses_addr;
no rows selected.
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发现没有活动事物后，drop回滚段。
接下来查找回滚段存储参数信息:
SQL> col tablespace_name format a10
SQL> col SEGMENT_NAME format a12
SQL> set line 120
SQL> select SEGMENT_NAME,OWNER,TABLESPACE_NAME,
initial_extent,NEXT_EXTENT,MIN_EXTENTS,MAX_EXTENTS,
PCT_INCREASE from dba_rollback_segs;
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SEGMENT_NAME OWNER? TABLESPACE INITIAL_EXTENT
NEXT_EXTENT MIN_EXTENTS MAX_EXTENTS PCT_INCREASE
------------ ------ ---------- -------------- ----------- -------
SYSTEM?????? SYS??? SYSTEM????????????? 57344?????? 57344????????
2???????? 505??????????? 0
RBS0???????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS1???????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS2???????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS3???????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS4???????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS5???????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS6???????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS7???????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS8???????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS9???????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS10??????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS11??????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS12??????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS13??????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS14??????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS15??????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS16??????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS17??????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS18??????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS19??????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS20??????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS21??????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS22??????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS23??????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS24??????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS26??????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS27??????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS28??????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
RBS25??????? PUBLIC RBS01????????????? 524288????? 524288????????
8??????? 4096??????????? 0
APPRBS?????? PUBLIC RBS01???????????? 2097152??? 10485760????????
50?????? 32765??????????? 0
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31 rows selected.
把initial_extent,next_extent,min_extents,max_extents,pct_increase的值都记录下来，留做以后创建新的回滚段使用。
