nologging是ORACLE提供的操作无日志选项，对于普通的INSERT 没有多少影响， 但如果INSERT的时候采用了/*+append*/，就会产生很少的日志
前提条件：非归档模式
测试如下（每次都是先删除表，再建表）
建表：
CREATE TABLE test1 AS SELECT * FROM dba_Objects WHERE 1>8 ;
表不作NOLOGGING处理：产生redo 8,697,536
SQL> SET ECHO OFF
SQL> SET VERIFY OFF
SQL> COLUMN VALUE NEW_VAL V
SQL> DEFINE S='&1'
SQL> SET AUTOTRACE OFF
Cannot SET AUTOTRACE
SQL> SELECT A.NAME,B.VALUE FROM V$STATNAME A ,V$MYSTAT B
2 WHERE A.STATISTIC#=B.STATISTIC#
3 AND LOWER(A.NAME) =LOWER('&S');
NAME VALUE
---------------------------------------------------------------- ----------
redo size 1124
SQL> INSERT INTO test1 SELECT * FROM dba_objects ;
72220 rows inserted
SQL>
SQL> set echo off
SQL> set verify off ;
SQL> select distinct a.name,&v 执行前 ,b.value 执行后,to_char(b.value-&v,'999,999,999,999') 操作产生的redo
2 from v$statname a ,v$mystat b
3 where a.statistic#=b.statistic#
4 and lower(a.name) =lower('&s');
NAME 执行前 执行后 操作产生的REDO
---------------------------------------------------------------- ---------- ---------- ----------------
redo size 1124 8698660 8,697,536
SQL>
SQL> SET ECHO OFF
SQL> SET VERIFY OFF
SQL> COLUMN VALUE NEW_VAL V
SQL> DEFINE S='&1'
SQL> SET AUTOTRACE OFF
Cannot SET AUTOTRACE
SQL> SELECT A.NAME,B.VALUE FROM V$STATNAME A ,V$MYSTAT B
2 WHERE A.STATISTIC#=B.STATISTIC#
3 AND LOWER(A.NAME) =LOWER('&S');
NAME VALUE
---------------------------------------------------------------- ----------
redo size 8698800
SQL> INSERT INTO test1 SELECT * FROM dba_objects nologging ;
72220 rows inserted
SQL>
SQL> set echo off
SQL> set verify off ;
SQL> select distinct a.name,&v 执行前 ,b.value 执行后,to_char(b.value-&v,'999,999,999,999') 操作产生的redo
2 from v$statname a ,v$mystat b
3 where a.statistic#=b.statistic#
4 and lower(a.name) =lower('&s');
NAME 执行前 执行后 操作产生的REDO
---------------------------------------------------------------- ---------- ---------- ----------------
redo size 8698800 17390924 8,692,124
对表进行nologging操作 产生redo 8,692,300 相对于不作处理，没有变化
SQL> alter table test1 nologging ;
Table altered
SQL>
SQL> SET ECHO OFF
SQL> SET VERIFY OFF
SQL> COLUMN VALUE NEW_VAL V
SQL> DEFINE S='&1'
SQL> SET AUTOTRACE OFF
Cannot SET AUTOTRACE
SQL> SELECT A.NAME,B.VALUE FROM V$STATNAME A ,V$MYSTAT B
2 WHERE A.STATISTIC#=B.STATISTIC#
3 AND LOWER(A.NAME) =LOWER('&S');
NAME VALUE
---------------------------------------------------------------- ----------
redo size 17393168
SQL> INSERT INTO test1 SELECT * FROM dba_objects ;
72220 rows inserted
SQL>
SQL> set echo off
SQL> set verify off ;
SQL> select distinct a.name,&v 执行前 ,b.value 执行后,to_char(b.value-&v,'999,999,999,999') 操作产生的redo
2 from v$statname a ,v$mystat b
3 where a.statistic#=b.statistic#
4 and lower(a.name) =lower('&s');
NAME 执行前 执行后 操作产生的REDO
---------------------------------------------------------------- ---------- ---------- ----------------
redo size 17393168 26085468 8,692,300
insert的时候，如果采用append 就会少很很多。 产生redo 66,600
SQL> SET ECHO OFF
SQL> SET VERIFY OFF
SQL> COLUMN VALUE NEW_VAL V
SQL> DEFINE S='&1'
SQL> SET AUTOTRACE OFF
Cannot SET AUTOTRACE
SQL> SELECT A.NAME,B.VALUE FROM V$STATNAME A ,V$MYSTAT B
2 WHERE A.STATISTIC#=B.STATISTIC#
3 AND LOWER(A.NAME) =LOWER('&S');
NAME VALUE
---------------------------------------------------------------- ----------
redo size 26085608
SQL> INSERT/*+append*/ INTO test1 SELECT * FROM dba_objects ;
72220 rows inserted
SQL>
SQL> set echo off
SQL> set verify off ;
SQL> select distinct a.name,&v 执行前 ,b.value 执行后,to_char(b.value-&v,'999,999,999,999') 操作产生的redo
2 from v$statname a ,v$mystat b
3 where a.statistic#=b.statistic#
4 and lower(a.name) =lower('&s');
NAME 执行前 执行后 操作产生的REDO
---------------------------------------------------------------- ---------- ---------- ----------------
redo size 26085608 26152208 66,600
如果再将表更改为nologging ，然后再insert的时候APPEND 会产生更少的REDO 26,472
SQL> alter table test1 nologging ;
Table altered
SQL>
SQL> SET ECHO OFF
SQL> SET VERIFY OFF
SQL> COLUMN VALUE NEW_VAL V
SQL> DEFINE S='&1'
SQL> SET AUTOTRACE OFF
Cannot SET AUTOTRACE
SQL> SELECT A.NAME,B.VALUE FROM V$STATNAME A ,V$MYSTAT B
2 WHERE A.STATISTIC#=B.STATISTIC#
3 AND LOWER(A.NAME) =LOWER('&S');
NAME VALUE
---------------------------------------------------------------- ----------
redo size 26162576
SQL> INSERT/*+append*/ INTO test1 SELECT * FROM dba_objects ;
72220 rows inserted
SQL>
SQL> set echo off
SQL> set verify off ;
SQL> select distinct a.name,&v 执行前 ,b.value 执行后,to_char(b.value-&v,'999,999,999,999') 操作产生的redo
2 from v$statname a ,v$mystat b
3 where a.statistic#=b.statistic#
4 and lower(a.name) =lower('&s');
NAME 执行前 执行后 操作产生的REDO
---------------------------------------------------------------- ---------- ---------- ----------------
redo size 26162576 26189048 26,472
测试条件：归档模式
以上结果大部分不会影响太大，只有append的时候会影响很大。
SQL> SET ECHO OFF
SQL> SET VERIFY OFF
SQL> COLUMN VALUE NEW_VAL V
SQL> DEFINE S='&1'
SQL> SET AUTOTRACE OFF
Cannot SET AUTOTRACE
SQL> SELECT A.NAME,B.VALUE FROM V$STATNAME A ,V$MYSTAT B
2 WHERE A.STATISTIC#=B.STATISTIC#
3 AND LOWER(A.NAME) =LOWER('&S');
NAME VALUE
---------------------------------------------------------------- ----------
redo size 8736356
SQL> INSERT/*+append*/ INTO test1 a SELECT * FROM dba_objects ;
72220 rows inserted
SQL>
SQL> set echo off
SQL> set verify off ;
SQL> select distinct a.name,&v 执行前 ,b.value 执行后,to_char(b.value-&v,'999,999,999,999') 操作产生的redo
2 from v$statname a ,v$mystat b
3 where a.statistic#=b.statistic#
4 and lower(a.name) =lower('&s');
NAME 执行前 执行后 操作产生的REDO
---------------------------------------------------------------- ---------- ---------- ----------------
redo size 8736356 17555000 8,818,644
这个区别也说明了，append只有在非归档模式下才会减少redo
