臨時(shí)表空間作用
Oracle臨時(shí)表空間主要用來(lái)做查詢(xún)和存放一些緩沖區(qū)數(shù)據(jù)。臨時(shí)表空間消耗的主要原因是需要對(duì)查詢(xún)的中間結(jié)果進(jìn)行排序。
重啟數(shù)據(jù)庫(kù)可以釋放臨時(shí)表空間，如果不能重啟實(shí)例，而一直保持問(wèn)題sql語(yǔ)句的執(zhí)行，temp表空間會(huì)一直增長(zhǎng)。直到耗盡硬盤(pán)空間。
網(wǎng)上有人猜測(cè)在磁盤(pán)空間的分配上，oracle使用的是貪心算法，如果上次磁盤(pán)空間消耗達(dá)到1GB，那么臨時(shí)表空間就是1GB。也就是說(shuō)當(dāng)前臨時(shí)表空間文件的大小是歷史上使用臨時(shí)表空間最大的大小。
臨時(shí)表空間的主要作用：
索引create或rebuild
Order by 或 group by
Distinct 操作
Union 或 intersect 或 minus
Sort-merge joins
analyze
查看臨時(shí)表空間大小
查看臨時(shí)表文件大小和已使用空間
select t1."Tablespace" "Tablespace",
t1."Total (G)" "Total (G)",
nvl(t2."Used (G)", 0) "Used(G)",
t1."Total (G)" - nvl(t2."Used (G)", 0) "Free (G)"
from
(
select tablespace_name "Tablespace", to_char((sum(bytes/1024/1024/1024)),'99,999,990.900') "Total (G)"
from dba_temp_files
group by tablespace_name
union
select tablespace_name "Tablespace", to_char((sum(bytes/1024/1024/1024)),'99,999,990.900') "Total (G)"
from dba_data_files
where tablespace_name like 'TEMP%'
group by tablespace_name
) t1,
(
select tablespace, round(sum(blocks)*8/1024) "Used (G)" from v$sort_usage
group by tablespace
) t2
where t1."Tablespace"=t2.tablespace(+)
查看當(dāng)前臨死表使用空間大小與正在占用臨時(shí)表空間的sql語(yǔ)句
select sess.SID, segtype, blocks*8/1000 "MB" ,sql_text
from v$sort_usage sort, v$session sess,v$sql sql
where sort.SESSION_ADDR = sess.SADDR
and sql.ADDRESS = sess.SQL_ADDRESS
order by blocks desc;
select 'the ' || name || ' temp tablespaces ' || tablespace_name ||
' idle ' ||
round(100 - (s.tot_used_blocks / s.total_blocks) * 100, 3) ||
'% at ' || to_char(sysdate, 'yyyymmddhh24miss')
from (select d.tablespace_name tablespace_name,
nvl(sum(used_blocks), 0) tot_used_blocks,
sum(blocks) total_blocks
from v$sort_segment v, dba_temp_files d
where d.tablespace_name = v.tablespace_name(+)
group by d.tablespace_name) s,
v$database;
修改臨時(shí)文件大小
select 'ALTER database TEMPFILE ' || file_name || ' resize 100M ;'
from dba_temp_files
where tablespace_name = 'ONLYDWTEMP';
ALTER database TEMPFILE '/oradata/ONLYDWTEMP06.dbf' resize 100M ;
ALTER database TEMPFILE '/oradata/ONLYDWTEMP07.dbf' resize 100M ;
ALTER database TEMPFILE '/oradata/ONLYDWTEMP08.dbf' resize 100M ;
ALTER database TEMPFILE '/oradata/ONLYDWTEMP09.dbf' resize 100M ;
ALTER database TEMPFILE '/oradata/ONLYDWTEMP10.dbf' resize 100M ;
ALTER database TEMPFILE '/oradata/ONLYDWTEMP01.dbf' resize 100M ;
ALTER database TEMPFILE '/oradata/ONLYDWTEMP02.dbf' resize 100M ;
ALTER database TEMPFILE '/oradata/ONLYDWTEMP03.dbf' resize 100M ;
ALTER database TEMPFILE '/oradata/ONLYDWTEMP04.dbf' resize 100M ;
ALTER database TEMPFILE '/oradata/ONLYDWTEMP05.dbf' resize 100M ;
SQL> ALTER database TEMPFILE '/oradata/ONLYDWTEMP09.dbf' resize 100M ;
ALTER database TEMPFILE '/oradata/ONLYDWTEMP09.dbf' resize 100M
ORA-03297: file contains used data beyond requested RESIZE value
創(chuàng)建新的臨時(shí)表空間
SQL> create temporary tablespace TEMP1 TEMPFILE '/oradata/TEMP1_01.dbf' size 100M;
Tablespace created
SQL> create temporary tablespace TEMP2 TEMPFILE '/oradata/TEMP2_01.dbf' size 100M;
Tablespace created
將當(dāng)前臨時(shí)表空間指定為新的臨時(shí)表空間
SQL> alter database default temporary tablespace TEMP1;
Database altered
刪除舊的臨時(shí)表空間
SQL> drop tablespace ONLYDWTEMP including contents and datafiles;
Tablespace dropped
檢查當(dāng)前用戶的臨時(shí)表空間
9i之前，如果一個(gè)數(shù)據(jù)庫(kù)用戶沒(méi)有被指定默認(rèn)臨時(shí)表空間，那么oracle就會(huì)使用system表空間作為該用戶的臨時(shí)表空間，這是很危險(xiǎn)的。在9i里邊，database可以被指定一個(gè)默認(rèn)臨時(shí)表空間。這樣如果數(shù)據(jù)庫(kù)用戶沒(méi)有被明確指定臨時(shí)表空間，oracle9i就會(huì)自動(dòng)指定database的默認(rèn)臨時(shí)表空間作為該用戶的臨時(shí)表空間。
我們可以通過(guò)下面的語(yǔ)句來(lái)查詢(xún)數(shù)據(jù)庫(kù)的默認(rèn)臨時(shí)表空間。
select * from database_properties where property_name = 'DEFAULT_TEMP_TABLESPACE';
如下語(yǔ)句可以查詢(xún)數(shù)據(jù)庫(kù)用戶的臨時(shí)表空間。
select username,default_tablespace,temporary_tablespace from dba_users
如果刪除了用戶的臨時(shí)表空間，而這個(gè)臨時(shí)表空間又不是默認(rèn)臨時(shí)表空間（如果是數(shù)據(jù)庫(kù)的默認(rèn)臨時(shí)表空間是刪不掉的），用戶的臨時(shí)表空間不會(huì)自動(dòng)轉(zhuǎn)換到數(shù)據(jù)庫(kù)的默認(rèn)臨時(shí)表空間上。這時(shí)如果使用該用戶登陸，并執(zhí)行查詢(xún)用到臨時(shí)空間，就會(huì)報(bào)錯(cuò)。解決方式就是將用戶的臨時(shí)表空間修改過(guò)來(lái)。
SQL> alter user CTL temporary tablespace TEMP1;
User altered
SQL> alter user ODS temporary tablespace TEMP2;
User altered
select username,default_tablespace,temporary_tablespace from dba_users
user
tablespace
temporary tablespace
SCOTT
SYSTEM
ONLYDWTEMP
CTL
CTL
TEMP1
ODS
ODSD
TEMP2
SQL> drop tablespace TEMP2 including contents and datafiles;
Tablespace dropped
select username,default_tablespace,temporary_tablespace from dba_users
user
tablespace
temporary tablespace
SCOTT
SYSTEM
ONLYDWTEMP
CTL
CTL
TEMP1
ODS
ODSD
TEMP2
Connected to Oracle9i Enterprise Edition Release 9.2.0.8.0
Connected as ods
SQL> select do.object_name from dba_objects do, dba_objects db order by 1;
Tablespace TEMP2 not found
SQL> alter user ODS temporary tablespace TEMP1;
User altered
以上的方法只是暫時(shí)釋放了臨時(shí)表空間的磁盤(pán)，是治標(biāo)但不是治本的方法。真正的治本方法是找出數(shù)據(jù)庫(kù)中消耗資源比較大的sql語(yǔ)句，然后對(duì)其進(jìn)行優(yōu)化處理。
Select se.username,
se.sid,
su.extents,
su.blocks * to_number(rtrim(p.value)) as Space,
tablespace,
segtype,
sql_text
from v$sort_usage su, v$parameter p, v$session se, v$sql s
where p.name = 'db_block_size'
and su.session_addr = se.saddr
and s.hash_value = su.sqlhash
and s.address = su.sqladdr
order by se.username, se.sid
