多次更新同一批记录,redo log也会依次增长

下面的试验证明了，每次更新都会产生redo log:

SQL> select b.name,a.value from v$mystat a, v$statname b
2 where a.STATISTIC#=b.STATISTIC#
3 and b.name ='redo size';

NAME VALUE
---------------------------------------------------------------- ----------
redo size 0

SQL> update table_1 set host_id=host_id+3;
已更新2122行。

SQL> select b.name,a.value from v$mystat a, v$statname b
2 where a.STATISTIC#=b.STATISTIC#
3 and b.name ='redo size';

NAME VALUE
---------------------------------------------------------------- ----------
redo size 924520

SQL> update table_1 set host_id=host_id+3;
已更新2122行。

SQL> select b.name,a.value from v$mystat a, v$statname b
2 where a.STATISTIC#=b.STATISTIC#
3 and b.name ='redo size';

NAME VALUE
---------------------------------------------------------------- ----------
redo size 1920784

SQL> commit;
提交完成。