alter table tab_name add partition

create table tsts_part1 (pkey NUMBER(9,0) DEFAULT -1) SEGMENT CREATION IMMEDIATE 
PARTITION BY LIST ("PKEY") 
(PARTITION "P00"  VALUES (0) , 
 PARTITION "P01"  VALUES (1) );
 
select * from v$parameter where name = 'deferred_segment_creation';
--deferred_segment_creation	=	TRUE

--check partitions without segment:
select partition_name 
from dba_tab_partitions
where table_name = 'TSTS_PART1'       
minus
select partition_name
from dba_segments
where segment_name = 'TSTS_PART1';
--none

alter table tsts_part1 add partition g02 values(2);
--check partitions without segment:
select partition_name 
from dba_tab_partitions
where table_name = 'TSTS_PART1'       
minus
select partition_name
from dba_segments
where segment_name = 'TSTS_PART1';
--still none

--same session:
create table tsts_part2 (pkey NUMBER(9,0) DEFAULT -1) --SEGMENT CREATION IMMEDIATE 
PARTITION BY LIST ("PKEY") 
(PARTITION "P00"  VALUES (0) , 
 PARTITION "P01"  VALUES (1) );
 
--check partitions without segment:
select partition_name 
from dba_tab_partitions
where table_name = 'TSTS_PART2'       
minus
select partition_name
from dba_segments
where segment_name = 'TSTS_PART2';
/*
P00
P01
*/

alter table tsts_part2 add partition p02 values(2);
--check partitions without segment:
select partition_name 
from dba_tab_partitions
where table_name = 'TSTS_PART2'       
minus
select partition_name
from dba_segments
where segment_name = 'TSTS_PART2';
/*
P00
P01
P02
*/