背景

  在上篇文章：http://blog.itpub.net/9240380/viewspace-1816241/，发现如果变更记录的列宽度变宽，会导致ora-01578错误，导致数据坏块。

结论

1,如果用bbed修改列宽度加大，会导致坏块出现
2,不知为何加大列宽度，会导致坏块出现，唉，还是对于数据块结构理解不深
3,在bbed中，可以用revert回退数据块的操作

测试

SQL> select * from t_bbed_modify_row;


A
--------------------
newly


SQL> select DBMS_ROWID.ROWID_RELATIVE_FNO(ROWID),DBMS_ROWID.ROWID_BLOCK_NUMBER(ROWID),dbms_rowid.rowid_row_number(rowid) from t_bbed_modify_row;


DBMS_ROWID.ROWID_RELATIVE_FNO(ROWID) DBMS_ROWID.ROWID_BLOCK_NUMBER(ROWID) DBMS_ROWID.ROWID_ROW_NUMBER(ROWID)
------------------------------------ ------------------------------------ ----------------------------------
                                   4                                99003                                  0


BBED> set file 4
        FILE#           4


BBED> set block 99003
        BLOCK#          99003




BBED> find /c newly
 File: /oracle/oradata/guowang/users01.dbf (4)
 Block: 99003            Offsets: 8183 to 8186           Dba:0x010182bb
------------------------------------------------------------------------
 6e65776c 


 <32 bytes per line>


可见不加count选项，默认仅显示列的前4位内容
 BBED> dump /v dba 4,99003
 File: /oracle/oradata/guowang/users01.dbf (4)
 Block: 99003   Offsets: 8183 to 8186  Dba:0x010182bb
-------------------------------------------------------
 6e65776c                            l newl


 <16 bytes per line>




 BBED> dump /v dba 4,99003 count 10
 File: /oracle/oradata/guowang/users01.dbf (4)
 Block: 99003   Offsets: 8183 to 8191  Dba:0x010182bb
-------------------------------------------------------
 6e65776c 79020665 fd                l newly..e.


 <16 bytes per line>


加上count则可以显示列的全部内容
 BBED> dump /v dba 4,99003 count 5
 File: /oracle/oradata/guowang/users01.dbf (4)
 Block: 99003   Offsets: 8183 to 8187  Dba:0x010182bb
-------------------------------------------------------
 6e65776c 79                         l newly


 <16 bytes per line>


修改列内容由newly奕成newlya
BBED> modify /c 'newlya' dba 4,99003 offset 8183
 File: /oracle/oradata/guowang/users01.dbf (4)
 Block: 99003            Offsets: 8183 to 8187           Dba:0x010182bb
------------------------------------------------------------------------
 6e65776c 79 


 <32 bytes per line>




BBED> dump /v dba 4,99003 count 6
 File: /oracle/oradata/guowang/users01.dbf (4)
 Block: 99003   Offsets: 8183 to 8188  Dba:0x010182bb
-------------------------------------------------------
 6e65776c 7961                       l newlya


 <16 bytes per line>


一验证就出现坏块了
 BBED> verify
Message 500 not found; No message file for product=RDBMS, facility=BBED
Message 501 not found; No message file for product=RDBMS, facility=BBED


Message 520 not found; No message file for product=RDBMS, facility=BBED
Corrupt block relative dba: 0x010182bb (file 0, block 99003)
Fractured block found during verification
Data in bad block:
 type: 6 format: 2 rdba: 0x010182bb
 last change scn: 0x0000.023bfd65 seq: 0x2 flg: 0x04
 spare1: 0x0 spare2: 0x0 spare3: 0x0
 consistency value in tail: 0xfd650661
 check value in block header: 0x4d80
 computed block checksum: 0x63


回退对于数据块的修改
BBED> revert
All changes made in this session will be rolled back. Proceed? (Y/N) y
Reverted file '/oracle/oradata/guowang/users01.dbf', block 99004
Reverted file '/oracle/oradata/guowang/users01.dbf', block 99003
Warning: contents of previous BIFILE will be lost. Proceed? (Y/N) y


确认数据没有损坏
SQL> select * from t_bbed_modify_row;


A
--------------------
newly


SQL> alter system flush buffer_cache;


System altered.


SQL> select * from t_bbed_modify_row;


A
--------------------
newly

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