11G延迟创建初始段

在初始化一个具有数千张表和索引的数据库时，每张表和索引都会设置分配10M的磁盘存储空间，这样会花费一些时间来完成Z这些DDL。
在11.2版本中，默认将表和索引的物理空间分配推迟到第一条记录插入到表中时。
且由参数deferred_segment_creation控制，
SQL> show parameter segment_crea

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
deferred_segment_creation boolean TRUE

也可在创建语句中segment creation immediate立即创建初始段,segment creation deferred延迟创建段空间

下面针对10G和11G做了简单测试：
11G:
[code][oracle@localhost ~]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.1.0 Production on Mon Dec 9 09:41:14 2013

Copyright (c) 1982, 2009, Oracle. All rights reserved.

Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> conn awen/oracle
Connected.
SQL> create table fbo_test_11g (id number,name varchar(2));

Table created.
SQL> select count(*) from dba_segments where segment_name ='FBO_TEST_11G';

COUNT(*)
----------
0

SQL> INSERT INTO fbo_test_11g values (1,'S');

1 row created.

SQL> select count(*) from dba_segments where segment_name ='FBO_TEST_11G';

COUNT(*)
----------
1

SQL> show parameter segment_crea

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
deferred_segment_creation boolean TRUE
[/code]
10G:
[code]C:\\Documents and Settings\\Administrator>sqlplus / as sysdba

SQL*Plus: Release 10.2.0.1.0 - Production on 星期一 12月 9 11:54:00 2013

Copyright (c) 1982, 2005, Oracle. All rights reserved.


连接到:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options

SQL> conn awen/oracle
已连接。
SQL> create table fbo_test (id number,name varchar2(10));

表已创建。

SQL> select count(*) from dba_segments where segment_name ='FBO_TEST';

COUNT(*)
----------
1

SQL> SHOW PARAMETER DEFERR
SQL> [/code]