create table as select 與create table後insert方式生成的undo與redo對比

      測試環境：OS:RHEL 5.4 X86  DB:10.2.0.4  歸檔模式

      下面是測試結論，此結論只是在本測試環境有效。

1，ctas與create table後insert語句產生的redo是差很少的。
2，ctas生成的undo遠遠小於create table and insert方式。
3，ctas生成的undo與create table後insert /*+ append */差很少。
4，ctas nologging方法生成的log遠遠小於其它的方式。
5，append方式並不必定能減小redo的生成，可是確定能減小undo的生成。
6，append減小redo，前提是表在nologging方式下面，注意這裏表上面沒有索引，append只對表有效，對索引無效。

     下面是詳細的測試步驟

1，ctas方式生成的undo與redo
SQL> SELECT a.name, b.VALUE
  2    FROM v$sysstat a, v$mystat b
  3   WHERE     a.statistic# = b.statistic#
  4         AND a.name IN ('redo size', 'undo change vector size');

NAME                                                                  VALUE
---------------------------------------------------------------- ----------
redo size                                                                 0
undo change vector size                                                   0
SQL> create table scott.test_ctas as select * from dba_objects;
SQL> /* Formatted on 2013/3/8 22:07:44 (QP5 v5.240.12305.39476) */
SQL> SELECT a.name, b.VALUE
  2    FROM v$sysstat a, v$mystat b
  3   WHERE     a.statistic# = b.statistic#
  4         AND a.name IN ('redo size', 'undo change vector size');

NAME                                                                  VALUE
---------------------------------------------------------------- ----------
redo size                                                           5794552
undo change vector size                                               23812

2，ctas nologging方式生成的undo與redo

SQL> SELECT a.name, b.VALUE
  2    FROM v$sysstat a, v$mystat b
  3   WHERE     a.statistic# = b.statistic#
  4         AND a.name IN ('redo size', 'undo change vector size');

NAME                                                                  VALUE
---------------------------------------------------------------- ----------
redo size                                                                 0
undo change vector size                                                   0

SQL> create table scott.test_ctas_nologging nologging as select * from dba_objects;

Table created.

SQL> SELECT a.name, b.VALUE
  2    FROM v$sysstat a, v$mystat b
  3   WHERE     a.statistic# = b.statistic#
  4         AND a.name IN ('redo size', 'undo change vector size');

NAME                                                                  VALUE
---------------------------------------------------------------- ----------
redo size                                                             88576
undo change vector size                                               22008

這種方式生成的UNDO,REDO的大小都是最好的，


3，普通表與insert生成的undo與redo

SQL> SELECT a.name, b.VALUE
  2    FROM v$sysstat a, v$mystat b
  3   WHERE     a.statistic# = b.statistic#
  4         AND a.name IN ('redo size', 'undo change vector size');

NAME                                                                  VALUE
---------------------------------------------------------------- ----------
redo size                                                                 0
undo change vector size                                                   0

SQL> create table scott.test_normal as select * from dba_objects where 1=0;

Table created.

SQL> SELECT a.name, b.VALUE
  2    FROM v$sysstat a, v$mystat b
  3   WHERE     a.statistic# = b.statistic#
  4         AND a.name IN ('redo size', 'undo change vector size');

NAME                                                                  VALUE
---------------------------------------------------------------- ----------
redo size                                                             19848
undo change vector size                                                5712

SQL> insert into scott.test_normal select * from dba_objects;

50350 rows created.

SQL> SELECT a.name, b.VALUE
  2    FROM v$sysstat a, v$mystat b
  3   WHERE     a.statistic# = b.statistic#
  4         AND a.name IN ('redo size', 'undo change vector size');

NAME                                                                  VALUE
---------------------------------------------------------------- ----------
redo size                                                           5725444
undo change vector size                                              208092


4，普通create表與insert append方式生成的redo與undo
SQL> SELECT a.name, b.VALUE
  2    FROM v$sysstat a, v$mystat b
  3   WHERE     a.statistic# = b.statistic#
  4         AND a.name IN ('redo size', 'undo change vector size');

NAME                                                                  VALUE
---------------------------------------------------------------- ----------
redo size                                                                 0
undo change vector size                                                   0

SQL> create table scott.test_normal_append as select * from dba_objects where 1=2;

Table created.

SQL> SELECT a.name, b.VALUE
  2    FROM v$sysstat a, v$mystat b
  3   WHERE     a.statistic# = b.statistic#
  4         AND a.name IN ('redo size', 'undo change vector size');

NAME                                                                  VALUE
---------------------------------------------------------------- ----------
redo size                                                             21224
undo change vector size                                                6072

SQL> insert /*+ append */ into scott.test_normal_append select * from dba_objects;

50350 rows created.

SQL> SELECT a.name, b.VALUE
  2    FROM v$sysstat a, v$mystat b
  3   WHERE     a.statistic# = b.statistic#
  4         AND a.name IN ('redo size', 'undo change vector size');

NAME                                                                  VALUE
---------------------------------------------------------------- ----------
redo size                                                           5771092
undo change vector size                                               21072

5，nologging方式的create表與insert append方式生成的undo與redo

SQL> SELECT a.name, b.VALUE
  2    FROM v$sysstat a, v$mystat b
  3   WHERE     a.statistic# = b.statistic#
  4         AND a.name IN ('redo size', 'undo change vector size');

NAME                                                                  VALUE
---------------------------------------------------------------- ----------
redo size                                                                 0
undo change vector size                                                   0

SQL> create table scott.test_normal_append_nologging nologging as select * from dba_objects where 1=2;

Table created.

SQL> SELECT a.name, b.VALUE
  2    FROM v$sysstat a, v$mystat b
  3   WHERE     a.statistic# = b.statistic#
  4         AND a.name IN ('redo size', 'undo change vector size');

NAME                                                                  VALUE
---------------------------------------------------------------- ----------
redo size                                                             37568
undo change vector size                                               14204

SQL> insert /*+ append */ into scott.test_normal_append_nologging select * from dba_objects;

50351 rows created.

SQL> SELECT a.name, b.VALUE
  2    FROM v$sysstat a, v$mystat b
  3   WHERE     a.statistic# = b.statistic#
  4         AND a.name IN ('redo size', 'undo change vector size');

NAME                                                                  VALUE
---------------------------------------------------------------- ----------
redo size                                                            142944
undo change vector size                                               46744