问题：怎么使用resize使表空间变小 或者说怎么让表空间resize到一个合理的值，并且腾出部分空间


查看当前块（标准块）大小

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SQL> set verify off
SQL> column file_name format a50 word_wrapped
SQL> column smallest format 999,990 heading "Smallest|Size|Poss."
SQL> column currsize format 999,990 heading "Current|Size"
SQL> column savings format 999,990 heading "Poss.|Savings"
SQL> break on report
SQL> compute sum of savings on report
SQL>
SQL> column value new_val blksize
SQL> select value from v$parameter where name = 'db_block_size';

VALUE
--------------------------------------------------------------------------------
8192
查看某个表空间可以收缩多少空间


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SQL> select file_name,
2 ceil( (nvl(hwm,1)*&&blksize)/1024/1024 ) smallest,
3 ceil( blocks*&&blksize/1024/1024) currsize,
4 ceil( blocks*&&blksize/1024/1024) -
5 ceil( (nvl(hwm,1)*&&blksize)/1024/1024 ) savings
6 from dba_data_files a,
7 ( select file_id, max(block_id+blocks+7) hwm
8 from dba_extents where tablespace_name='TEST'
9 group by file_id ) b
10 where a.file_id = b.file_id(+) and tablespace_name='TEST';

Smallest
Size Current Poss.
FILE_NAME Poss. Size Savings
-------------------------------------------------- -------- -------- --------
/oracle/app/oracle/oradata/mydb/test01.dbf 139 2,048 1,909
/backup/test02.dbf 36 1,024 988
--------
sum 2,897 --可以腾出空间的总大小2897M
生成操作语句

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SQL> column cmd format a75 word_wrapped
SQL> select 'alter database datafile '''||file_name||''' resize ' ||
2 ceil( (nvl(hwm,1)*&&blksize)/1024/1024 ) || 'm;' cmd
3 from dba_data_files a,
4 ( select file_id, max(block_id+blocks+7) hwm
5 from dba_extents where tablespace_name='TEST'
6 group by file_id ) b
7 where b.file_id = a.file_id(+)
8 and ceil( blocks*&&blksize/1024/1024) -
9 ceil( (nvl(hwm,1)*&&blksize)/1024/1024 ) > 0;

CMD
---------------------------------------------------------------------------
alter database datafile '/backup/test02.dbf' resize 36m;
alter database datafile '/oracle/app/oracle/oradata/mydb/test01.dbf' resize
139m

执行上述resize命令，表空间变小，可以为其他表空间分配空间了