行迁移消除中的疑问！

gy1982329

exp和imp可以将行迁移删除！我不太理解！为什么这样做能实现！请斑竹和高人从理论和实际层面加以讲解！谢谢！

ehxz

1.执行
utlchain.sql脚本
SQL> CREATE TABLE chained_rows (
  2  owner_name         VARCHAR2(30),
  3  table_name         VARCHAR2(30),
  4  cluster_name       VARCHAR2(30),
  5  partition_name     VARCHAR2(30),
  6  head_rowid         ROWID,
  7  analyze_timestamp  DATE );
创建chained_rows表，然后分析
SQL> ANALYZE TABLE oe.orders LIST CHAINED ROWS;
Table analyzed.
SQL> SELECT  owner_name, table_name, head_rowid
  2    FROM  chained_rows
  3    WHERE table_name = 'ORDERS';
OWNER_NAME  TABLE_NAME  HEAD_ROWID        
----------  ----------  ------------------
SALES       ORDER_HIST  AAAAluAAHAAAAA1AAA
SALES       ORDER_HIST  AAAAluAAHAAAAA1AAB
2.对行迁移的处理
  a).exp/drop/imp table
  b).alter table emp move ...;
  c).查找迁移的行，拷贝迁移的行到一个新表，删除原记录，然后从新表将行拷贝到原表
3.相关的脚本

/* Get the name of the table with migrated rows */
ACCEPT table_name PROMPT 'Enter the name of the table with migrated rows: '
/* Clean up from last execution */
SET ECHO OFF
DROP TABLE migrated_rows;
DROP TABLE chained_rows;
/* Create the CHAINED_ROWS table */
@?/rdbms/admin/utlchain
SET ECHO ON
SPOOL fix_mig
/* List the chained & migrated rows */
ANALYZE TABLE &table_name LIST CHAINED ROWS;
------------------------------------------------------------------------

/* Copy the chained/migrated rows to another table */
CREATE TABLE migrated_rows AS
  SELECT orig.*
  FROM &table_name orig, chained_rows cr
  WHERE orig.rowid = cr.head_rowid
  AND cr.table_name = upper('&table_name');
/* Delete the chained/migrated rows from the original table */
DELETE FROM &table_name
WHERE rowid IN (
  SELECT head_rowid
  FROM chained_rows);
/* Copy the chained/migrated rows back into the original table */
INSERT INTO &table_name
  SELECT *
  FROM migrated_rows;
SPOOL OFF

参考一下，不知道是否能用上。

gy1982329

我的意思是，导入和导出是如何实现对行迁移的删除的！后台进行了什么操作或是如何实现的！我想知道原理！谢谢