Need help on sql

Hi ,

I have an column called comments in COMMENTS table which is an CLOB column, I need to change the column data type from CLOB to VARCHAR2. Below is the code

DROP TABLE COMM_INTERIM;

CREATE TABLE COMM_INTERIM
   (      COMMENTARY_ID NUMBER ,
      SUBJECT VARCHAR2(400 CHAR) ,
      COMMENTS varchar2(4000 char),
      CREATED_BY NUMBER ,
      LAST_MODIFIED_DATE DATE,
      CREATED_DATE DATE ,
      LAST_MODIFIED_BY NUMBER ,
      VISIBILITY_TYPE NUMBER ,
      DEAL_GROUP_ID NUMBER ,
      LOCK_VERSION NUMBER ,
      VISIBILITY_RESOURCE_ID NUMBER ,
      DEAL_ID NUMBER,
      TRANCHE_ID NUMBER,
      ORGANIZATION1_ID NUMBER,
      ORGANIZATION1_MEMBER_ID NUMBER,
      ORGANIZATION2_ID NUMBER,
      ORGANIZATION2_MEMBER_ID NUMBER,
      ORGANIZATION3_ID NUMBER,
      ORGANIZATION3_MEMBER_ID NUMBER,
      EXTERNAL_ID VARCHAR2(100 CHAR),
      LEVEL_OF_ACCESS_ID NUMBER
   );


 Declare
col_mapping varchar2 (2000);
BEGIN
--  map all the columns in the interim table to the original table
col_mapping :=

                'COMMENTARY_ID COMMENTARY_ID , ' ||
    'SUBJECT SUBJECT , ' ||
    'DBMS_LOB.SUBSTR(COMMENTS,1,4000) COMMENTS , '||
    'CREATED_BY CREATED_BY, LAST_MODIFIED_DATE LAST_MODIFIED_DATE,'
    ||'CREATED_DATE CREATED_DATE , LAST_MODIFIED_BY LAST_MODIFIED_BY ,VISIBILITY_TYPE VISIBILITY_TYPE ,'    
    ||'DEAL_GROUP_ID DEAL_GROUP_ID,LOCK_VERSION LOCK_VERSION,VISIBILITY_RESOURCE_ID VISIBILITY_RESOURCE_ID,'||
    'DEAL_ID DEAL_ID,TRANCHE_ID TRANCHE_ID,ORGANIZATION1_ID ORGANIZATION1_ID,ORGANIZATION1_MEMBER_ID ORGANIZATION1_MEMBER_ID,'
    ||'ORGANIZATION2_ID ORGANIZATION2_ID,ORGANIZATION2_MEMBER_ID ORGANIZATION2_MEMBER_ID,ORGANIZATION3_ID ORGANIZATION3_ID,'
    ||'ORGANIZATION3_MEMBER_ID ORGANIZATION3_MEMBER_ID,EXTERNAL_ID EXTERNAL_ID,LEVEL_OF_ACCESS_ID LEVEL_OF_ACCESS_ID';
   
               
dbms_redefinition.start_redef_table('SCOTT', 'COMMENTS', 'COMM_INTERIM', col_mapping);
END;
/


declare
error_count pls_integer := 0;
BEGIN
  dbms_redefinition.copy_table_dependents('SCOTT', 'COMMENTS', 'COMM_INTERIM',
                                          1, true,true,true,false,
                                          error_count);

  dbms_output.put_line('errors := ' || to_char(error_count));
END;
/


exec  dbms_redefinition.finish_redef_table('SCOTT', 'COMMENTS', 'COMM_INTERIM');
/

After running the above script file geting the below error, any help is really appreciated.

Table created.


PL/SQL procedure successfully completed.


PL/SQL procedure successfully completed.


PL/SQL procedure successfully completed.

declare
*
ERROR at line 1:
ORA-23540: Redefinition not defined or initiated
ORA-06512: at "SYS.DBMS_SYS_ERROR", line 79
ORA-06512: at "SYS.DBMS_REDEFINITION", line 1809
ORA-06512: at line 4