ORACLE中表空间和表碎片的示例分析
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表空间碎片率
idle> select a.tablespace_name,sqrt(max(a.blocks)/sum(a.blocks))*(100/sqrt(sqrt(count(a.blocks)))) FSFI
from dba_free_space a,dba_tablespaces b
where a.tablespace_name=b.tablespace_name
and b.contents not in ('TEMPORARY','UNDO')
group by a.tablespace_name
order by 2;
TABLESPACE_NAME FSFI
------------------------------ ----------
EAM 2.57604251ALM 20.1734462SYSAUX 22.2842767SYSTEM 23.7809729USERS 53.439579RECCAT 100ARCH 1007 rows selected.
idle>
123456789101112131415161718192021数字越小，表空间碎片较多，当小于30%的时候说明碎片程度很可观了。
按照表空间显示连续的空闲时间
引用官方的一段话：
The ideal situation is to have one large free extent in your tablespace. The more extents of free space there are in the tablespace, the more likely you will run into fragmentation problems. The size of the free extents is also very important. If you have a lot of small extents (too small for any next extent size) but the total bytes of free space is large, then you may want to consider defragmentation options.
脚本中统计了连续空间及对连续空间求和，当表中的总的free空间很大时，但有很多小块，说明碎片化越严重。
======== Script : tfstsfgm ========SET ECHO off REM NAME:TFSTSFRM.SQL REM USAGE:"@path/tfstsfgm" REM ------------------------------------------------------------------------ REM REQUIREMENTS: REM SELECT ON DBA_FREE_SPACE REM ------------------------------------------------------------------------ REM PURPOSE: REM The following is a script that will determine how many extents REM of contiguous free space you have in Oracle as well as the REM total amount of free space you have in each tablespace. From REM these results you can detect how fragmented your tablespace is. REM REM The ideal situation is to have one large free extent in your REM tablespace. The more extents of free space there are in the REM tablespace, the more likely you will run into fragmentation REM problems. The size of the free extents is also very important. REM If you have a lot of small extents (too small for any next REM extent size) but the total bytes of free space is large, then REM you may want to consider defragmentation options. REM ------------------------------------------------------------------------ REM DISCLAIMER: REM This script is provided for educational purposes only. It is NOT REM supported by Oracle World Wide Technical Support. REM The script has been tested and appears to work as intended. REM You should always run new scripts on a test instance initially. REM ------------------------------------------------------------------------ REM Main text of script follows: create table SPACE_TEMP ( TABLESPACE_NAME CHAR(30), CONTIGUOUS_BYTES NUMBER) / declare cursor query is select * from dba_free_space order by tablespace_name, block_id; this_row query%rowtype; previous_row query%rowtype; total number; begin open query; fetch query into this_row; previous_row := this_row; total := previous_row.bytes; loop fetch query into this_row; exit when query%notfound; if this_row.block_id = previous_row.block_id + previous_row.blocks then total := total + this_row.bytes; insert into SPACE_TEMP (tablespace_name) values (previous_row.tablespace_name); else insert into SPACE_TEMP values (previous_row.tablespace_name, total); total := this_row.bytes; end if; previous_row := this_row; end loop; insert into SPACE_TEMP values (previous_row.tablespace_name, total); end; . / set pagesize 60 set newpage 0 set echo off ttitle center 'Contiguous Extents Report' skip 3 break on "TABLESPACE NAME" skip page duplicate spool contig_free_space.lis rem column "CONTIGUOUS BYTES" format 999,999,999 column "COUNT" format 999 column "TOTAL BYTES" format 999,999,999 column "TODAY" noprint new_value new_today format a1 rem select TABLESPACE_NAME "TABLESPACE NAME", CONTIGUOUS_BYTES "CONTIGUOUS BYTES" from SPACE_TEMP where CONTIGUOUS_BYTES is not null order by TABLESPACE_NAME, CONTIGUOUS_BYTES desc; select tablespace_name, count(*) "# OF EXTENTS", sum(contiguous_bytes) "TOTAL BYTES" from space_temp group by tablespace_name; spool off drop table SPACE_TEMP / 1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798
表空间级别整理方法
对于ASSM管理的表空间，一般都是由smon进程自动整理，前提是表空间的pctincrease值为非0，可以将表空间的缺省存储参数pctincrease改为非0，一般将其设为1。如修改temp表空间的pctincrease属性：alter tablespace temp default storage(pctincrease 1); 这样就可以自动整理表空间级别的碎片整理了。
如果对于字典管理的表空间，可以用下面的命令进行整理：
sql> alter tablespace <表空间名> collesce;
表级别碎片整理方法
1.首选shrink
SQL> alter table t1 enable row movement; --打开行移动表已更改。 SQL> alter table t1 shrink space cascade; --压缩表及相关数据段并下调HWMSQL> alter table t1 shrink space compact; --只压缩不下调HWMSQL> alter table t1 shrink space ; --下调HWMSQL> alter table t1 disable row movement; --关闭行移动1234567891011
只能在ASSM、本地管理的表空间进行，完成这些之后不需要进行索引的重建，但统计信息最好重新收集下，脚本参加本博客上上篇。^_^
2.导入导出
用exp/imp导出后，重新导入重建，在重新创建索引和重新收集统计信息。
3.CATS技术
create table newtable as select * from old_table
drop old_table
rename table newtable to old_table
重建索引，收集统计信息。
4.move tablespace
sql> alter table <表名> move tablespace <表空间名> 重建索引，收集统计信息。123
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文章标题：ORACLE中表空间和表碎片的示例分析
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