11.2.0.2中引入了_partition_large_extents 的新特性，在extent size auto allocate的表空间上若创建分区表，则分区的initial extent size为8M。 试看下面的例子：
_partition_large_extents
TRUE
Enables large extent allocation for partitioned tables
_index_partition_large_extents
FALSE
Enables large extent allocation for partitioned indices
SQL> select ALLOCATION_TYPE from dba_tablespaces where tablespace_name='USERS';
ALLOCATION_TYPE
------------------
SYSTEM
@partition.sql ==》测试用CREATE TABLE脚本，将在users表空间上创建一个有384个子分区的表
alter session set deferred_segment_creation=false;
SQL> select count(*) from dba_tab_subpartitions where table_name='MACLEAN_PARTITION';
COUNT(*)
----------
384
SQL> select blocks,count(*) from dba_Extents where segment_name='MACLEAN_PARTITION' group by blocks;
BLOCKS COUNT(*)
---------- ----------
1024 384
SQL> alter session set "_partition_large_extents"=false;
会话已更改。
@partition.sql
SQL> select count(*) from dba_tab_subpartitions where table_name='MACLEAN_PARTITION';
COUNT(*)
----------
384
SQL> select blocks,count(*) from dba_Extents where segment_name='MACLEAN_PARTITION' group by blocks;
BLOCKS COUNT(*)
---------- ----------
8 384
可以看到在11.2.0.2 以后_partition_large_extents参数默认打开(default : TRUE)， 且当表空间allocation_type=SYSTEM时
本文转自maclean_007 51CTO博客，原文链接:http://blog.51cto.com/maclean/1278497
