【11gR2新特性】Large Partition Extents:_partition_large_extents & _index_partition_large_extents

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