Drop column from compressed table

Question

NLSRTL
11.2.0.3.0
Production
Oracle Database 11g Enterprise Edition
11.2.0.3.0
64bit Production
PL/SQL
11.2.0.3.0
Production
TNS for Linux:
11.2.0.3.0
Production
Hello,
I read about how to drop column from a compressed table - first set it unused and then drop the unused columns. However, in the example below on the database I ran it, it does not work. Please, can you tell me WHEN this approach does not work. What it is dependent on - parameters or something else. Why I cannot drop the unused columns?
And the example along with the errors:
create table tcompressed compress as select * from all_users;
> table TCOMPRESSED created.
alter table tcompressed add x number;
> table TCOMPRESSED altered.
alter table tcompressed drop column x;
>
Error report:
SQL Error: ORA-39726: unsupported add/drop column operation on compressed tables
39726. 00000 -  "unsupported add/drop column operation on compressed tables"
*Cause:    An unsupported add/drop column operation for compressed table
           was attemped.
*Action:   When adding a column, do not specify a default value.
           DROP column is only supported in the form of SET UNUSED column
           (meta-data drop column).
alter table tcompressed set unused column x;
> table TCOMPRESSED altered.
alter table tcompressed drop unused columns;
>
Error report:
SQL Error: ORA-39726: unsupported add/drop column operation on compressed tables
39726. 00000 -  "unsupported add/drop column operation on compressed tables"
*Cause:    An unsupported add/drop column operation for compressed table
           was attemped.
*Action:   When adding a column, do not specify a default value.
           DROP column is only supported in the form of SET UNUSED column
           (meta-data drop column).
As you can see even after altering the table by setting the column X as unused I still cannot drop it by using DROP UNUSED COLUMNS.
Thank you.

Answer 1

check this link it might help. At the end it has also mentioned of a bug check the same.
http://sharpcomments.com/2008/10/ora-39726-unsupported-adddrop-column-operation-on-compressed-tables.html