简述收缩表空间的办法

我们来看一下如何收缩表空间，其实方法很简单。*先我们先计算datafile可以resize收缩的空间.col name for a40col 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;' ResizeCMDfrom v$datafile a,     (select file_id,max(block_id+blocks-1) HWM       from dba_extents       group by file_id) bwhere a.file# = b.file_id(+)and (a.bytes - HWM *block_size)>0order by 5

如果只是想对某个表个间的datafile resize,可采用: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;' ResizeCMDfrom 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) bwhere a.file# = b.file_id(+)and (a.bytes - HWM *block_size)>0order by 5

计划tempfile可以resize的空间.on apply that have only one tempfile

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