转自惜总文章:http://ask.orasos.com/thread-11-1-1.html
set verify off
column file_name format a50 word_wrapped
column smallest format 999,990 heading "Smallest|Size|Poss."
column currsize format 999,990 heading "Current|Size"
column savings format 999,990 heading "Poss.|Savings"
break on report
compute sum of savings on report
column value new_val blksize
select value from v$parameter where name = 'db_block_size'
/
select file_name,ceil( (nvl(hwm,1)*&&blksize)/1024/1024 ) smallest,ceil( blocks*&&blksize/1024/1024) currsize,ceil( blocks*&&blksize/1024/1024) -
ceil( (nvl(hwm,1)*&&blksize)/1024/1024 ) savings
from dba_data_files a,( select file_id,max(block_id+blocks-1) hwm
from dba_extents
group by file_id ) b
where a.file_id = b.file_id(+)
/
column cmd format a75 word_wrapped
select 'alter database datafile '''||file_name||''' resize ' ||
ceil( (nvl(hwm,1)*&&blksize)/1024/1024 ) || 'm;' cmd
from dba_data_files a,max(block_id+blocks-1) hwm
from dba_extents
group by file_id ) b
where a.file_id = b.file_id(+)
and ceil( blocks*&&blksize/1024/1024) -
ceil( (nvl(hwm,1)*&&blksize)/1024/1024 ) > 0
请注意:以上脚本针对如下情况,不能回收全部的空间:
比如一个10个GB的datafile,已经使用第2GB 和第9GB,从表空间使用率的角度看,Free空间是8GB,用以上脚本仅仅能回收的空间肯定是远远小于8GB.
因为,resize的过程只是缩小Datafile的大小,resize并不负责移动数据库对象(table 或者index)
