DBV(DBVERIFY)是Oracle提供的一个命令行工具，它可以对数据文件物理和逻辑两种一致性检查。但是这个工具不会检查索引记录和数据记录的匹配关系，这种检查必须使用analyze validate structure命令。
这个工具有如下特点：
以只读的方式打开数据文件，在检查过程中不会修改数据文件的内容。
可以在线检查数据文件，而不需要关闭数据库。
不能检查控制文件和日志文件，只能检查数据文件。
这个工具可以检查ASM文件，但数据库必须Open状态，并且需要通过USERID指定用户，比如：dbv file=+DG1/ORCL/datafile/system01.dbf userid=system/sys
在许多UNIX平台下，DBV要求数据文件有扩展名，如果没有可以通过建立链接的方法，然后对链接的方法，然后对链接文件进行操作，比如：ls -n /dev/rdsk/mydevice /tmp/mydevice.dbf
某些平台，DBV工具不能检查超过2GB的文件，如果碰到DBV-100错误，请先检查文件大小，MOS Bug 710888对这个问题有描述。
DBV只会检查数据块的正确性，但不会关系数据块是否属于哪个对象。
对于祼设备建议指定END参数，避免超出数据文件范围。比如：dbv FILE=/dev/rdsk/r1.dbf END=<last_block_number>。可以在v$datafile视图中用bytes字段除以块大小来获得END值。
参数 含义 缺省值FILE 要检查的数据文件名 没有缺省值
START 检查起始数据块号 数据文件的第一个数据块
END 检查的最后一个数据块号 数据文件的最后一个数据块
BLOCKSIZE 数据块大小，这个值要和数据库的DB_BLOCK_SIZE参数值一致 缺省值8192
LOGFILE 检查结果日志文件 没有缺省值
FEEDBAK 显示进度 0
PARFILE 参数文件名 没有缺省值
USERID 用户名、密码 没有缺省值
SEGMENT_ID 段ID，参数格式<tsn.segfile.segblock> 没有缺省值
使用示例：
[oracle@rhel6 ~]$ dbv file=/u01/app/oracle/oradata/test/users01.dbf
DBVERIFY: Release 11.2.0.1.0 - Production on Mon May 22 16:42:26 2017
Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved.
DBVERIFY - Verification starting : FILE = /u01/app/oracle/oradata/test/users01.dbf
DBVERIFY - Verification complete
Total Pages Examined : 155520
Total Pages Processed (Data) : 144530
Total Pages Failing (Data) : 0
Total Pages Processed (Index): 52
Total Pages Failing (Index): 0
Total Pages Processed (Other): 1248
Total Pages Processed (Seg) : 0
Total Pages Failing (Seg) : 0
Total Pages Empty : 9690
Total Pages Marked Corrupt : 0
Total Pages Influx : 0
Total Pages Encrypted : 0
Highest block SCN : 3559792 (0.3559792)
这个工具报告使用的是page作为单位，含义和data block相同。从上面的检查结果Total Pages Marked Corrupt : 0可以看出文件没有坏块。
除了检查数据文件，这个工具还允许检查单独的Segment，这时参数值的格式为<tsn.segfile.segblock>
查看对象的tsn,segfile,segblock属性：
zx@TEST>select t.ts#,s.header_file,s.header_block
2 from v$tablespace t,dba_segments s
3 where s.segment_name='T'
4 and t.name=s.tablespace_name;
TS# HEADER_FILE HEADER_BLOCK
---------- ----------- ------------
4 4 45834
从上面的查询结果可行参数值为4.4.45834。检查Segment：
[oracle@rhel6 ~]$ dbv userid=system/123456 segment_id=4.4.45834
DBVERIFY: Release 11.2.0.1.0 - Production on Mon May 22 20:58:33 2017
Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved.
DBVERIFY - Verification starting : SEGMENT_ID = 4.4.45834
DBVERIFY - Verification complete
Total Pages Examined : 8
Total Pages Processed (Data) : 5
Total Pages Failing (Data) : 0
Total Pages Processed (Index): 0
Total Pages Failing (Index): 0
Total Pages Processed (Other): 2
Total Pages Processed (Seg) : 1
Total Pages Failing (Seg) : 0
Total Pages Empty : 0
Total Pages Marked Corrupt : 0
Total Pages Influx : 0
Total Pages Encrypted : 0
Highest block SCN : 3518579 (0.3518579)
下面人为创造一个坏块，用dbv来检查。
创建一个测试表
zx@TEST>create table bbed (id number,name varchar2(20)) tablespace users;
Table created.
zx@TEST>insert into bbed values(1,'zhaoxu');
1 row created.
zx@TEST>commit;
Commit complete.
当前数据文件没有坏块
[oracle@rhel6 ~]$ dbv file=/u01/app/oracle/oradata/test/users01.dbf
DBVERIFY: Release 11.2.0.1.0 - Production on Mon May 22 21:03:40 2017
Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved.
DBVERIFY - Verification starting : FILE = /u01/app/oracle/oradata/test/users01.dbf
DBVERIFY - Verification complete
Total Pages Examined : 155520
Total Pages Processed (Data) : 66397
Total Pages Failing (Data) : 0
Total Pages Processed (Index): 52
Total Pages Failing (Index): 0
Total Pages Processed (Other): 88898
Total Pages Processed (Seg) : 0
Total Pages Failing (Seg) : 0
Total Pages Empty : 173
Total Pages Marked Corrupt : 0
Total Pages Influx : 0
Total Pages Encrypted : 0
Highest block SCN : 3764775 (0.3764775)
获取表在文件中的存储信息
zx@TEST>set serveroutput on
zx@TEST>declare rfno number;
2 rtype number;
3 ono number;
4 blkno number;
5 rowno number;
6 rid varchar2(30);
7 begin
8 select rowid into rid from bbed;
9 dbms_rowid.rowid_info(ROWID_IN=>rid,RELATIVE_FNO=>rfno,BLOCK_NUMBER=>blkno,ROW_NUMBER=>rowno,ROWID_TYPE=>rtype,OBJECT_NUMBER=>ono);
10 dbms_output.put_line(rfno||','||blkno||','||rowno);
11 end;
12 /
4,45844,0
PL/SQL procedure successfully completed.
使用bbed修改块信息
[oracle@rhel6 bbed]$ bbed parfile=bbed.par
Password:
BBED: Release 2.0.0.0.0 - Limited Production on Mon May 22 21:17:18 2017
Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved.
************* !!! For Oracle Internal Use only !!! ***************
BBED> set dba 4,45844
DBA 0x0100b314 (16823060 4,45844)
BBED> find /c zhaoxu
File: /u01/app/oracle/oradata/test/users01.dbf (4)
Block: 45844 Offsets: 8182 to 8191 Dba:0x0100b314
------------------------------------------------------------------------
7a68616f 78750106 5873
<32 bytes per line>
BBED> dump /v dba 4,45844 offset 8182 count 32
File: /u01/app/oracle/oradata/test/users01.dbf (4)
Block: 45844 Offsets: 8182 to 8191 Dba:0x0100b314
-------------------------------------------------------
7a68616f 78750106 5873 l zhaoxu..Xs
<16 bytes per line>
BBED> modify 100 dba 4,45844
Warning: contents of previous BIFILE will be lost. Proceed? (Y/N) y
File: /u01/app/oracle/oradata/test/users01.dbf (4)
Block: 45844 Offsets: 8182 to 8191 Dba:0x0100b314
------------------------------------------------------------------------
6468616f 78750106 5873
<32 bytes per line>
BBED> dump /v dba 4,45844 offset 8182 count 32
File: /u01/app/oracle/oradata/test/users01.dbf (4)
Block: 45844 Offsets: 8182 to 8191 Dba:0x0100b314
-------------------------------------------------------
6468616f 78750106 5873 l dhaoxu..Xs
<16 bytes per line>
BBED> exit
再次使用dbv检查文件
[oracle@rhel6 bbed]$ dbv file=/u01/app/oracle/oradata/test/users01.dbf
DBVERIFY: Release 11.2.0.1.0 - Production on Mon May 22 21:18:46 2017
Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved.
DBVERIFY - Verification starting : FILE = /u01/app/oracle/oradata/test/users01.dbf
Page 45844 is marked corrupt
Corrupt block relative dba: 0x0100b314 (file 4, block 45844)
Bad check value found during dbv:
Data in bad block:
type: 6 format: 2 rdba: 0x0100b314
last change scn: 0x0000.00397358 seq: 0x1 flg: 0x04
spare1: 0x0 spare2: 0x0 spare3: 0x0
consistency value in tail: 0x73580601
check value in block header: 0x7c2d
computed block checksum: 0x1e
DBVERIFY - Verification complete
Total Pages Examined : 155520
Total Pages Processed (Data) : 66396
Total Pages Failing (Data) : 0
Total Pages Processed (Index): 52
Total Pages Failing (Index): 0
Total Pages Processed (Other): 88898
Total Pages Processed (Seg) : 0
Total Pages Failing (Seg) : 0
Total Pages Empty : 173
Total Pages Marked Corrupt : 1
Total Pages Influx : 0
Total Pages Encrypted : 0
Highest block SCN : 3764775 (0.3764775)
报告一个坏块，Total Pages Marked Corrupt : 1
再次查询测试表：
sys@TEST>select * from zx.bbed;
ID NAME
---------- ------------------------------------------------------------
1 zhaoxu
查询正常，因为在buffer_cache中缓存了块，而修改的是文件中的块。两个块现在不一致，清空buffer cache后再次查询测试表。
zx@TEST>alter system flush buffer_cache;
System altered.
zx@TEST>select * from bbed;
select * from bbed
*
ERROR at line 1:
ORA-01578: ORACLE data block corrupted (file # 4, block # 45844)
ORA-01110: data file 4: '/u01/app/oracle/oradata/test/users01.dbf'
查询报出错误ORA-01578。
使用dbv检查ASM文件中的数据文件，需要指定userid参数
[oracle@rac1 ~]$ dbv file=+DATA/orcl/datafile/users.259.925306091 userid=sys/123456
DBVERIFY: Release 11.2.0.4.0 - Production on Mon May 22 16:48:22 2017
Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.
DBVERIFY - Verification starting : FILE = +DATA/orcl/datafile/users.259.925306091
DBVERIFY - Verification complete
Total Pages Examined : 640
Total Pages Processed (Data) : 16
Total Pages Failing (Data) : 0
Total Pages Processed (Index): 2
Total Pages Failing (Index): 0
Total Pages Processed (Other): 593
Total Pages Processed (Seg) : 0
Total Pages Failing (Seg) : 0
Total Pages Empty : 29
Total Pages Marked Corrupt : 0
Total Pages Influx : 0
Total Pages Encrypted : 0
Highest block SCN : 0 (0.0)