[oracle@rhel63single ~]$ sqlplus scott/aaaaaa

sql*Plus: Release 11.2.0.4.0 Production on Sat Apr 8 02:54:40 2017

Copyright (c) 1982,2013,Oracle.  All rights reserved.

Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning,Automatic Storage Management,OLAP,Data Mining
and Real Application Testing options

sql> show parameter defer

NAME				     TYPE	 VALUE
------------------------------------ ----------- ------------------------------
deferred_segment_creation	     boolean	 TRUE
sql> create table testa(reg_id number,reg_name varchar2(200)) segment creation immediate;

Table created.

sql> create table testb(reg_id number,reg_name varchar2(200)) ;

Table created.

sql> create table testc(reg_id number,reg_name varchar2(200)) segment creation deferred;

Table created.

sql> select segment_name from user_segments where segment_name in( 'TESTA','TESTB','TESTC');

SEGMENT_NAME
--------------------------------------------------------------------------------
TESTA

sql> select segment_name from user_extents where segment_name in( 'TESTA','TESTC');

SEGMENT_NAME
--------------------------------------------------------------------------------
TESTA

sql> 

总结: 1.create table的参数 segment creation immediate 的优先级高于数据库初始化参数deferred_segment_creation 2.create table的参数 segment creation immediate 的反义参数是segment creation deferred