-- Lets consider this Locally Managed tablespace with UNIFORM extent sizes(INITIAL=NEXT=64k)

thiru@9.2.0:SQL>select * from dba_Tablespaces where tablespace_name='LOCAL_UNIFORM';

TABLESPACE_NAME      BLOCK_SIZE INITIAL_EXTENT NEXT_EXTENT MIN_EXTENTS MAX_EXTENTS PCT_INCREASE MIN_EXTLEN S
-------------------- ---------- -------------- ----------- ----------- ----------- ------------ ---------- -
LOGGING   FOR EXTENT_MAN ALLOCATIO PLU SEGMEN
--------- --- ---------- --------- --- ------
LOCAL_UNIFORM              4096          65536       65536           1  2147483645            0      65536 O
LOGGING   NO  LOCAL      UNIFORM   NO  MANUAL

thiru@9.2.0:SQL>drop table t2;

Table dropped.

thiru@9.2.0:SQL>create table t2 (x int) storage(initial 1m next 1m minextents 5) tablespace local_uniform;
create table t2 (x int) storage(initial 1m next 1m minextents 5) tablespace local_uniform
*
ERROR at line 1:
ORA-01542: tablespace 'LOCAL_UNIFORM' is offline, cannot allocate space in it

thiru@9.2.0:SQL>alter tablespace local_uniform online;

Tablespace altered.

-- Lets create a table specifying (similar to the import) the initial,next,minextents in this tablespace

thiru@9.2.0:SQL>create table t2 (x int) storage(initial 1m next 1m minextents 5) tablespace local_uniform;

Table created.

thiru@9.2.0:SQL>select * from user_Segments where segment_name='T2';

SEGMENT_NAME                   PARTITION_NAME                 SEGMENT_TYPE       TABLESPACE_NAME           B
------------------------------ ------------------------------ ------------------ -------------------- ------
   EXTENTS INITIAL_EXTENT NEXT_EXTENT MIN_EXTENTS MAX_EXTENTS PCT_INCREASE  FREELISTS FREELIST_GROUPS BUFFER
---------- -------------- ----------- ----------- ----------- ------------ ---------- --------------- ------
T2                                                            TABLE              LOCAL_UNIFORM           524
        80        5242880       65536           1  2147483645            0          1               1 DEFAUL

-- As seen above,the size of the INITIAL_EXTENT is shown as the sum of the minextents(5*1M) of the table created. The NEXT_EXTENT is 64k however.

-- But look at the number of extents. It is 80 , not 5,which tells us that we have 80 * 64k extents allocated and not 5*1m extents ( ie as per the tablespace definition and not per the table specification).

thiru@9.2.0:SQL>select 65536*80 from dual;

  65536*80
----------
   5242880
-- and this (ie 5M) is the size of the table.

thiru@9.2.0:SQL>analyze table t2 compute statistics;

Table analyzed.

thiru@9.2.0:SQL>select initial_Extent,next_Extent,blocks from user_Tables where table_name='T2';

INITIAL_EXTENT NEXT_EXTENT     BLOCKS
-------------- ----------- ----------
       5242880       65536          0

thiru@9.2.0:SQL>

alter table T move tablespace LOCAL_UNIFORM;