ORA-32793: cannot alter a system-generated sequence

create table tq84_ora_32793 (
   id  integer generated by default as identity primary key,
   val varchar2(20) not null 
);
 
begin
   insert into tq84_ora_32793 (id, val) values ( 7, 'ABC');
   insert into tq84_ora_32793 (id, val) values ( 2, 'DEF');
   insert into tq84_ora_32793 (id, val) values ( 4, 'GHI');
  
   commit;
end;
/
 
begin
   insert into tq84_ora_32793 (val) values ('IJK');
   insert into tq84_ora_32793 (val) values ('LMN');
   insert into tq84_ora_32793 (val) values ('OPQ');
  
   commit;
end;
/
-- ORA-00001: unique constraint (DWH_DM_ABS.SYS_C001450294) violated
-- See Problems with GENERATED BY DEFAULT ON NULL AS IDENTITY columns
 
 
select
   idc.sequence_name
from
   user_tab_identity_cols idc
where
   idc.table_name = 'TQ84_ORA_32793' and
   idc.column_name = 'ID';
--
-- ISEQ$$_11993184
  
select max(id) + 1 nextval from tq84_ora_32793 ;
--
-- 8
 
alter sequence ISEQ$$_11993184 restart start with 8;
--
-- ORA-32793: cannot alter a system-generated sequence
 
alter table tq84_ora_32793 modify id generated by default as identity start with 8;
 
begin
   insert into tq84_ora_32793 (val) values ('IJK');
   insert into tq84_ora_32793 (val) values ('LMN');
   insert into tq84_ora_32793 (val) values ('OPQ');
  
   commit;
end;
/
 
select * from tq84_ora_32793 order by id;
 
drop table tq84_ora_32793;