CTAS、Nologging以及数据库运行模式

iputb讨论链接:

http://www.itpub.net/showthread.php?threadid=242761

我们看以下测试:

SQL> archive log list
Database log mode No Archive Mode
Automatic archival Enabled
Archive destination /opt/oracle/oradata/hsjf/archive
Oldest online log sequence 156
Current log sequence 158
SQL> @redo
SQL> select * from redo_size;

VALUE
----------
80892

SQL> create table test nologging as select * from dba_objects;

Table created.

SQL> select * from redo_size;

VALUE
----------
118024

SQL> drop table test;

Table dropped.

SQL> select * from redo_size;

VALUE
----------
139732

SQL> create table test as select * from dba_objects;

Table created.

SQL> select * from redo_size;

VALUE
----------
176864

SQL> select (176864 -139732) redo2,(118024 -80892) redo1 from dual;

REDO2 REDO1
---------- ----------
37132 37132

SQL> drop table test;

Table dropped.

SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.

Total System Global Area 235999908 bytes
Fixed Size 451236 bytes
Variable Size 201326592 bytes
Database Buffers 33554432 bytes
Redo Buffers 667648 bytes
Database mounted.
SQL> alter database archivelog;

Database altered.

SQL> alter database open;

Database altered.

SQL> @redo
SQL> select * from redo_size;

VALUE
----------
35768

SQL> create table test nologging as select * from dba_objects;

Table created.

SQL> select * from redo_size;

VALUE
----------
73860

SQL> drop table test;

Table dropped.

SQL> select * from redo_size;

VALUE
----------
95596

SQL> create table test as select * from dba_objects;

Table created.

SQL> select * from redo_size;

VALUE
----------
1215092

SQL> select (1215092 -95596) redo2,(73860 -35768) from dual;

REDO2 (73860-35768)
---------- -------------
1119496 38092
.

结论:

显然ctas的Nologging在archivelog模式下才会不记录redo，而在Noarchivelog模式下会产生同样多的redo
在归档模式下的CTAS nologging应该等价于非归档模式下ctas + insert append