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