实验: Oracle中表shrink与move产生redo日志比较
实验: Oracle中表shrink与move产生redo日志比较
1 move时实验
SQL> create table my_objects_move tablespace ASSM as select * from all_objects where rownum
Table created
SQL> select value
2 from v$mystat, v$statname
3 where v$mystat.statistic# = v$statname.statistic#
4 and v$statname.name = 'redo size';
VALUE
----------
2317832
SQL> delete from my_objects_move where object_name like '%C%';
7546 rows deleted
SQL> delete from my_objects_move where object_name like '%U%';
2959 rows deleted
SQL> commit;
Commit complete
SQL> select value
2 from v$mystat, v$statname
3 where v$mystat.statistic# = v$statname.statistic#
4 and v$statname.name = 'redo size';
VALUE
----------
6159912
SQL> alter table my_objects_move move;
Table altered
SQL> select value
2 from v$mystat, v$statname
3 where v$mystat.statistic# = v$statname.statistic#
4 and v$statname.name = 'redo size';
VALUE
----------
7265820
SQL> select (7265820 - 6159912) / 1024 / 1024 "redo_size(M)" from dual;
redo_size(M)
------------
1.0546760559
2 shrink时实验
SQL> create table my_objects tablespace ASSM as select * from all_objects where rownum
Table created
SQL> select value
2 from v$mystat, v$statname
3 where v$mystat.statistic# = v$statname.statistic#
4 and v$statname.name = 'redo size';
VALUE
----------
2315104
SQL> delete from my_objects where object_name like '%C%';
7546 rows deleted
SQL> delete from my_objects where object_name like '%U%';
2959 rows deleted
SQL> commit;
Commit complete
SQL> select value
2 from v$mystat, v$statname
3 where v$mystat.statistic# = v$statname.statistic#
4 and v$statname.name = 'redo size';
VALUE
----------
6157428
SQL> alter table my_objects enable row movement;
Table altered
SQL> alter table my_objects shrink space;
Table altered
SQL> select value
2 from v$mystat, v$statname
3 where v$mystat.statistic# = v$statname.statistic#
4 and v$statname.name = 'redo size';
VALUE
----------
11034900
SQL> select (11034900 - 6157428) / 1024 / 1024 "redo_size(M)" from dual;
redo_size(M)
------------
4.6515197753
3 结论
move时产生的日志比shrink时少．