create table ane_t1(a varchar2(2000));
 
Table created

create index ane_t1$a on ane_t1(a);
 
Index created

insert into ane_t1 select rpad(rownum,2000,'x') from dual connect by level < 1000;
 
999 rows inserted

commit;
 
Commit complete

select segment_type, segment_name, bytes,blocks,extents from dba_segments where segment_name like 'ANE_T1$A';
 
SEGMENT_TYPE       SEGMENT_NA      BYTES     BLOCKS    EXTENTS
------------------ ---------- ---------- ---------- ----------
INDEX              ANE_T1$A      4194304        512         19

insert into ane_t1 select rpad('b'||rownum,2000,'x') from dual connect by level < 1000;
 
999 rows inserted

commit;
 
Commit complete

select segment_type, segment_name, bytes,blocks,extents from dba_segments where segment_name like 'ANE_T1$A';
 
SEGMENT_TYPE       SEGMENT_NA      BYTES     BLOCKS    EXTENTS
------------------ ---------- ---------- ---------- ----------
INDEX              ANE_T1$A      8388608       1024         23

-- Удалим "пол-таблицы логов"
delete ane_t1 where a < '999z';
 
997 rows deleted

commit;
 
Commit complete

select segment_type, segment_name, bytes,blocks,extents from dba_segments where segment_name like 'ANE_T1$A';
 
SEGMENT_TYPE       SEGMENT_NA      BYTES     BLOCKS    EXTENTS
------------------ ---------- ---------- ---------- ----------
INDEX              ANE_T1$A      8388608       1024         23

-- вставим справа
insert into ane_t1 select rpad('c'||rownum,2000,'x') from dual connect by level < 1000;
 
999 rows inserted

commit;
 
Commit complete

select segment_type, segment_name, bytes,blocks,extents from dba_segments where segment_name like 'ANE_T1$A';
 
SEGMENT_TYPE       SEGMENT_NA      BYTES     BLOCKS    EXTENTS
------------------ ---------- ---------- ---------- ----------
INDEX              ANE_T1$A      8388608       1024         23

drop table ane_t1 purge;
 
Table dropped
 
SQL>