模拟插入数据
create table test as select * from dba_objects;
insert into test select * from test;
insert into test select * from test;
insert into test select * from test;
commit;
收集统计信息
SET TIME ON
exec dbms_stats.gather_table_stats(ownname=>'TEST',tabname=> 'TEST',DEGREE=>2);
查询初始表的碎片率68126
SELECT table_name,
ROUND ( (blocks * 8), 2) "HW_space k",
ROUND ( (num_rows * avg_row_len / 1024), 2) "real_space k",
ROUND ( (blocks * 10 / 100) * 8, 2) "(pctfree) k",
ROUND (
( blocks * 8
- (num_rows * avg_row_len / 1024)
- blocks * 8 * 10 / 100),
2)
"waste_space k"
FROM user_tables
WHERE temporary = 'N' AND TABLE_NAME='TEST'
--and OWNER='TEST'
ORDER BY 5 DESC;TABLE_NAME HW_space k real_space k (pctfree) k waste_space k
---------- ---------- ------------ ----------- -------------
TEST 89176 68126.08 8917.6 12132.32
第一次模拟清理数据
delete from test where object_type in('SYNONYM','JAVA CLASS');
commit;
再次收集统计信息
SET TIME ON
exec dbms_stats.gather_table_stats(ownname=>'TEST',tabname=> 'TEST',DEGREE=>2);
第一次清理完查询表的碎片率18963
TABLE_NAME HW_space k real_space k (pctfree) k waste_space k
---------- ---------- ------------ ----------- -------------
TEST 89176 18963.03 8917.6 61295.37
第二次模拟删除数据
delete from test where object_type in('VIEW','INDEX','TABLE','TYPE');
commit;
再次收集统计信息
SET TIME ON
exec dbms_stats.gather_table_stats(ownname=>'TEST',tabname=> 'TEST',DEGREE=>2);
第二次清理完查询表的碎片率6199，但是可以看到浪费的空间一直在增加74058.9，高水位一直没有变化89176
TABLE_NAME HW_space k real_space k (pctfree) k waste_space k
---------- ---------- ------------ ----------- -------------
TEST 89176 6199.5 8917.6 74058.9
进行表碎片整理
15:21:46 SQL> alter table test enable row movement;Table altered.15:24:52 SQL> alter table test shrink space;Table altered.15:25:23 SQL> exec dbms_stats.gather_table_stats(ownname=>'TEST',tabname=> 'TEST',DEGREE=>2);PL/SQL procedure successfully completed.15:25:47 SQL> SELECT table_name,
15:25:56 2 ROUND ( (blocks * 8), 2) "HW_space k",
15:25:56 3 ROUND ( (num_rows * avg_row_len / 1024), 2) "real_space k",
15:25:56 4 ROUND ( (blocks * 10 / 100) * 8, 2) "(pctfree) k",
15:25:56 5 ROUND (
15:25:56 6 ( blocks * 8
15:25:56 7 - (num_rows * avg_row_len / 1024)
15:25:56 8 - blocks * 8 * 10 / 100),
2)
15:25:56 9 15:25:56 10 "waste_space k"
FROM user_tables
15:25:56 11 15:25:56 12 WHERE temporary = 'N' AND TABLE_NAME='TEST'
15:25:56 13 --and OWNER='TEST'
15:25:56 14 ORDER BY 5 DESC;TABLE_NAME HW_space k real_space k (pctfree) k waste_space k
---------- ---------- ------------ ----------- -------------
TEST 7408 6199.5 740.8 467.7
经过以上表碎片整理之后，可以看到表的高水位已经降下来7408，浪费的空间已经得到释放467.7
