缩小数据文件Oracle

缩小数据文件

• 查看数据文件能缩小的最小值

• ceil 函数：返回大于或等于 n 的最小整数

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(+) order by savings desc
/

• 缩小数据文件的大小

SQL> alter database datafile '/oracle/app/oradata/ORCL/data01.dbf' resize 3800M;

Database altered.

• 如果低于HWM，则会出现以下报错

SQL> alter database datafile '/oracle/app/oradata/ORCL/data01.dbf' resize 3700M;
 alter database datafile '/oracle/app/oradata/ORCL/data01.dbf' resize 3700M
*
ERROR at line 1:
ORA-03297: file contains used data beyond requested RESIZE value