ORA-14450: attempt to access a transactional temp table already in use

Step to resolve this error.

1)Lock the table in exclusive mode

sql>lock table <username>.<temp_table> in exclusive mode;

2)Leave this session as it is and take new session

3) Take another session and execute below command

sql>SELECT * FROM v$lock
    WHERE id1 = (SELECT object_id FROM all_objects WHERE owner =<schema_name> AND object_name =<glb temp table>);

sql>ALTER SYSTEM KILL SESSION '<sid>,<serial#>';

4)After all the session get killed (confirm once)

5)perform the DDL on table;

sql>ALTER TABLE <username>.<temp_table>MODIFY(CONVERSION_FACTOR_VAL NUMBER (20,9));

6)Release the lock which we held in step (1) by below command

sql>rollback;