做一个 initial 大于 uniform size 乘以 minextents 的实验,总结出initial extent的分配规律

本文是原创文章，转载请注明出处：

做一个 INITIAL EXTENT 大于 UNIFORM size 乘以 MINEXTENTS 的实验。总结出initial extent的分配规律

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

SQL> alter system set deferred_segment_creation=false;

System altered.

SQL> show parameter defer

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
deferred_segment_creation            boolean     FALSE

SQL> create tablespace test_uni_sz_1m
  2  datafile '/u01/app/oracle/oradata/test/test_uni_sz_1m_01.dbf' size 200m
  3  extent management local uniform size 1m;

Tablespace created.

SQL> create table test_tab_3 (col1 varchar2(2)) tablespace test_uni_sz_1m storage(initial 10m minextents 3); 

Table created.

SQL> select bytes from dba_extents where segment_name = 'TEST_TAB_3' and owner = 'SCOTT';

     BYTES
----------
   1048576
   1048576
   1048576
   1048576
   1048576
   1048576
   1048576
   1048576
   1048576
   1048576
   1048576

     BYTES
----------
   1048576

12 rows selected.

SQL> show user
USER is "SCOTT"
SQL>

结果是分配了12个大小为1M（即：uniform size）的 extents。

貌似是前10个 1M 对应minextents的第一个， 后2个1M对应 minextents的第二个和第三个。