DATAFILE SHRINK释放系统空间

寄语：datafile Shrink来释放系统空间。下面是一些脚本，希望对大家有所帮助。

##环境##
SQL> select * from v$version;

BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
PL/SQL Release 11.2.0.4.0 - Production
CORE 11.2.0.4.0 Production
TNS for IBM/AIX RISC System/6000: Version 11.2.0.4.0 - Production
NLSRTL Version 11.2.0.4.0 - Production

##查看datafile resize 最小值（Smallest Size Poss.）##

Script for MAX-Shrink:-
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
/

                                                 Smallest
                                                       Size Current    Poss.
FILE_NAME                                             Poss.     Size Savings
-------------------------------------------------- -------- -------- --------
+DATA/ggdb/datafile/bigfile_pgs_data_index.dbf             1 153,600 153,599
+DATA/ggdb/datafile/bigfile_dm_data_index.dbf             1   51,200   51,199
+DATA/ggdb/datafile/pgs_data_tbs_10                  23,900   32,704    8,804
+DATA/ggdb/datafile/pgs_data_tbs_08                  26,298   32,704    6,406

##查看datafile HWM和datafile tablespace_name##
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,
     ( select file_id, 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
/

TABLESPACE_NAME FILE_NAME                                          FILE_SIZE    HWM CAN_SAVE
--------------- -------------------------------------------------- --------- ------ --------
BBMC_pgs_TEST   +DATA/ggdb/datafile/BBMC_pgs_test01.dbf                  346    346        0
BBMC_pgs_TEST   +DATA/ggdb/datafile/BBMC_pgs_test02.dbf                  329    329        0
BIONE_DATA      +DATA/ggdb/datafile/bione_data_01.dbf                    200      5      195
cmdc_DATA_TBS    +DATA/ggdb/datafile/cmdc_data_tbs_01.dbf                32760 32561      199

##批量生成datafile resize语句##
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,
     ( select file_id, 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
/

CMD
---------------------------------------------------------------------------
alter database datafile '+DATA/ggdb/datafile/pgs_data_tbs_16.dbf' resize 25661m;
alter database datafile '+DATA/ggdb/datafile/pgs_data_tbs_08' resize 26298m;
alter database datafile '+DATA/ggdb/datafile/pgs_data_tbs_01.dbf' resize 29565m;
alter database datafile '+DATA/ggdb/datafile/pgs_data_tbs_10.dbf' resize 32703m;

总结：DBA维护当中，多多使用脚本来提升效率。

本文参考：
How to SHRINK or Reduce the datafile size by finding the HWM (文档 ID 1600774.1)
http://blog.chinaunix.net/uid-42518-id-2404799.html

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Oracle 11g DATAFILE SHRINK 释放系统空间