Oracle計算datafile能夠resize收縮的空間

有時數據庫服務器磁盤空間在不知不覺中已經不夠用了，當數據庫沒法使用報錯時，須要緊急恢復，再進行轉移或磁盤擴容，這時能夠臨時釋放必定磁盤空間，保障數據庫正常運行

計算datafile能夠resize收縮的空間.
col name for a40
col resizecmd for a80

select a.file#,a.name,a.bytes/1024/1024 CurrentMB,
       ceil(HWM * a.block_size)/1024/1024 ResizeTo,
       (a.bytes - HWM * a.block_size)/1024/1024 ReleaseMB,
       'alter database datafile '''||a.name||''' resize '||
       ceil(HWM * a.block_size/1024/1024) || 'M;' ResizeCMD
from v$datafile a,
     (select file_id,max(block_id+blocks-1) HWM
       from dba_extents
       group by file_id) b
where a.file# = b.file_id(+)
and (a.bytes - HWM *block_size)>0
order by 5

若是隻是想對某個表個間的datafile resize,可採用:
select a.file#,a.name,a.bytes/1024/1024 CurrentMB,
       ceil(HWM * a.block_size)/1024/1024 ResizeTo,
       (a.bytes - HWM * a.block_size)/1024/1024 ReleaseMB,
       'alter database datafile '''||a.name||''' resize '||
       ceil(HWM * a.block_size/1024/1024) || 'M;' ResizeCMD
from v$datafile a,
     (select file_id,max(block_id+blocks-1) HWM
       from dba_extents where file_id in 
              (select b.file#  From v$tablespace a ,v$datafile b
                where a.ts#=b.ts# and a.name='MP2000')
       group by file_id) b
where a.file# = b.file_id(+)
and (a.bytes - HWM *block_size)>0
order by 5


計劃tempfile能夠resize的空間.on apply that have only one tempfile

select 'alter database tempfile '''||a.name ||''' reize '||b.siz||'M;' from v$tempfile a,
     (select tmsize.maxblk*bk.value/1024/1024 siz from
         (select nvl(max(segblk#),128) maxblk  from v$sort_usage) tmsize,
         (select value From v$parameter where name = 'db_block_size') bk) b