Workaround for ORA-00997: illegal use of LONG datatype

You'll need to create your target table explicitly, not from select *:

create table demo_copy
( table_name varchar2(30)
, column_name varchar2(30)
, data_type varchar2(106)
, data_type_mod varchar2(3)
, data_type_owner varchar2(30)
, data_length number
, data_precision number
, data_scale number
, nullable varchar2(1)
, column_id number
, default_length number
, data_default clob
, num_distinct number
, low_value raw(32)
, high_value raw(32)
, density number
, num_nulls number
, num_buckets number
, last_analyzed date
, sample_size number
, character_set_name varchar2(44)
, char_col_decl_length number
, global_stats varchar2(3)
, user_stats varchar2(3)
, avg_col_len number
, char_length number
, char_used varchar2(1)
, v80_fmt_image varchar2(3)
, data_upgraded varchar2(3)
, hidden_column varchar2(3)
, virtual_column varchar2(3)
, segment_column_id number
, internal_column_id number
, histogram varchar2(15)
, qualified_col_name varchar2(4000) );

(I've made data_default a clob for more convenient querying.)

Then you can insert rows in a PL/SQL loop:

begin
    for r in (
        select * from user_tab_cols c
        where  rownum <= 2  -- your filter condition here
    )
    loop
        insert into demo_copy values r;
    end loop;
end;

There are some limitations in principle with this approach, as a long column can hold more than the varchar2(32760) that PL/SQL will use in the loop. However, I expect 32K will be enough for most column default expressions.

ORA-00997: illegal use of LONG datatype

It is a restriction on usage of LONG data type. You cannot create an object type with a LONG attribute.

SQL> CREATE TABLE t AS SELECT data_default FROM user_tab_cols;
CREATE TABLE t AS SELECT data_default FROM user_tab_cols
                         *
ERROR at line 1:
ORA-00997: illegal use of LONG datatype


SQL>

Alternatively, you could use TO_LOB as a workaround. Which would convert it into CLOB data type.

For example,

SQL> CREATE TABLE t AS SELECT TO_LOB(data_default) data_default FROM user_tab_cols;

Table created.

SQL> desc t;
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 DATA_DEFAULT                                       CLOB

SQL>

See more examples of workarounds here.