在有些情况下，比如存储空间不足了，数据文件创建时指定过大了。可能会需要对数据文件的大小进行调整，这时可以执行下脚本，产生resize的命令，来方便对数据文件进行减小操作。

sql> @C:\Users\bb30\Documents\IT\Scripts\oracle\resize_datafile.sql
==========DATAFILE INFO:

FILE_NAME                                                    BLOCK_SIZE_KB SMALLEST_MB CURRSIZE_MB SAVINGS_MB
------------------------------------------------------------ ------------- ----------- ----------- ----------
C:\ORACLE\ORADATA\ORCL11GR2\SYSTEM01.DBF                                 8         752         752       0
C:\ORACLE\ORADATA\ORCL11GR2\SYSAUX01.DBF                                 8         493         520      27
C:\ORACLE\ORADATA\ORCL11GR2\USERS01.DBF                                  8          15          15       0
C:\ORACLE\ORADATA\ORCL11GR2\EXAMPLE01.DBF                                8         313         313       0
C:\ORACLE\ORADATA\ORCL11GR2\UNDOTBS01.DBF                                8          84          85       1
C:\ORACLE\ORADATA\ORCL11GR2\TB_16K_01.DBF                               16           2          10       8
C:\ORACLE\ORADATA\ORCL11GR2\USERS02.DBF                                  8           1           2       1

7 rows selected.

==========RESIZE CMD:

CMD
------------------------------------------------------------------------------------------
alter database datafile 'C:\ORACLE\ORADATA\ORCL11GR2\SYSAUX01.DBF' resize 493m;
alter database datafile 'C:\ORACLE\ORADATA\ORCL11GR2\UNDOTBS01.DBF' resize 84m;
alter database datafile 'C:\ORACLE\ORADATA\ORCL11GR2\TB_16K_01.DBF' resize 2m;
alter database datafile 'C:\ORACLE\ORADATA\ORCL11GR2\USERS02.DBF' resize 1m;