CTAS、Nologging以及数据库运行模式的详细介绍
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
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