如果对并发要求很高，那么还可以选择在线重定义的方式来转换LONG列：

SQL> CREATE TABLE T
  2  (ID NUMBER,
  3  CONTENTS LONG);

Table created.

SQL> INSERT INTO T
  2  SELECT ROWNUM, OWNER || OBJECT_NAME || OBJECT_TYPE
  3  FROM ALL_OBJECTS;

75338 rows created.

SQL> COMMIT;

Commit complete.

SQL> ALTER TABLE T ADD PRIMARY KEY (ID);

Table altered.

下面建立中间表，并利用在线重定义的方式来转换LONG到CLOB类型：

SQL> CREATE TABLE T_INTER
  2  (ID NUMBER,
  3  CONTENTS CLOB);

Table created.

SQL> SET SERVEROUT ON SIZE 100000
SQL> EXEC DBMS_REDEFINITION.CAN_REDEF_TABLE(USER, 'T')

PL/SQL procedure successfully completed.

SQL> EXEC DBMS_REDEFINITION.START_REDEF_TABLE(USER, 'T', 'T_INTER', 'ID ID, TO_LOB(CONTENTS) CONTENTS')

PL/SQL procedure successfully completed.

SQL> DECLARE
  2  V_NUM NUMBER;
  3  BEGIN
  4  DBMS_REDEFINITION.COPY_TABLE_DEPENDENTS(USER, 'T', 'T_INTER', DBMS_REDEFINITION.CONS_ORIG_PARAMS, TRUE, TRUE, TRUE, TRUE, V_NUM, TRUE);
  5  DBMS_OUTPUT.PUT_LINE(V_NUM);
  6  END;
  7  /
0

PL/SQL procedure successfully completed.

SQL> EXEC DBMS_REDEFINITION.FINISH_REDEF_TABLE(USER, 'T', 'T_INTER')

PL/SQL procedure successfully completed.

SQL> DESC T
 Name                                          Null?    Type
 --------------------------------------------- -------- ------------------------
 ID                                                     NUMBER
 CONTENTS                                               CLOB

SQL> DESC T_INTER
 Name                                          Null?    Type
 --------------------------------------------- -------- -------------------------
 ID                                            NOT NULL NUMBER
 CONTENTS                                               LONG

这种方式也不复杂，而且锁表的时间更断，更适合7*24的环境。

Oracle给出的方法还包括EXP/EXPDB的方式，不过这种方式借助导出、导入工具，而且在删除表后还要手工创建表，再执行导入，并没有性能和操作简单度上的优势，这里就不讨论了。