以下是一个缩小datafile大小的例子

oracle@JAB2:~/oradata/irdex> pwd
/opt/oracle/oradata/irdex
oracle@JAB2:~/oradata/irdex> ll
total 65021612
drwxr-xr-x  2 oracle oinstall       36864 2014-09-25 12:38 archive
-rw-r-----  1 oracle oinstall     1859584 2014-09-25 15:10 control01.ctl
-rw-r-----  1 oracle oinstall     1859584 2014-09-25 15:10 control02.ctl
-rw-r-----  1 oracle oinstall     1859584 2014-09-25 15:10 control03.ctl
-rw-r-----  1 oracle oinstall    52436992 2014-09-25 13:09 drsys01.dbf
-rw-r-----  1 oracle oinstall    26222592 2014-09-25 13:09 indx01.dbf
-rw-r-----  1 oracle oinstall  2147491840 2014-09-25 15:09 irdex01.dbf
-rw-r-----  1 oracle oinstall  2147491840 2014-09-25 15:10 irdex02.dbf
-rw-r-----  1 oracle oinstall  2147491840 2014-09-25 15:09 irdex03.dbf
-rw-r-----  1 oracle oinstall  4194312192 2014-09-25 13:09 irdex_arch01.dbf
-rw-r-----  1 oracle oinstall  4194312192 2014-09-25 13:09 irdex_arch02.dbf
-rw-r-----  1 oracle oinstall  4194312192 2014-09-25 13:09 irdex_arch03.dbf
-rw-r-----  1 oracle oinstall  4194312192 2014-09-25 13:09 irdex_arch04.dbf
-rw-r-----  1 oracle oinstall  4131397632 2014-09-25 13:09 irdex_arch05.dbf
-rw-r-----  1 oracle oinstall  4156563456 2014-09-25 13:09 irdex_arch06.dbf
-rw-r-----  1 oracle oinstall 20971528192 2014-09-25 13:09 irdex_arch07.dbf
-rw-r-----  1 oracle oinstall 10485768192 2014-09-25 13:09 irdex_arch08.dbf
-rw-r-----  1 oracle oinstall   104858112 2014-09-25 15:10 redo01.log
-rw-r-----  1 oracle oinstall   104858112 2014-09-25 09:42 redo02.log
-rw-r-----  1 oracle oinstall   104858112 2014-09-25 12:38 redo03.log
-rw-r-----  1 oracle oinstall   104858112 2014-09-25 06:55 redo04.log
-rw-r-----  1 oracle oinstall   524296192 2014-09-25 15:06 system01.dbf
-rw-r-----  1 oracle oinstall   419438592 2014-09-20 03:01 temp01.dbf
-rw-r-----  1 oracle oinstall   524296192 2014-09-25 13:09 tools01.dbf
-rw-r-----  1 oracle oinstall  1634738176 2014-09-25 15:09 undotbs01.dbf
-rw-r-----  1 oracle oinstall    52436992 2014-09-25 13:09 users01.dbf
-rw-r-----  1 oracle oinstall   104865792 2014-09-25 13:09 xdb01.dbf

Connected to Oracle9i Enterprise Edition Release 9.2.0.6.0
Connected as irdex

SQL> truncate table  IRDEX_ARCH.ARCH_IRDEX_MSGDATA;

Table truncated

SQL> alter database  datafile '/opt/oracle/oradata/irdex/irdex_arch08.dbf' resize 4000m;

Database altered

SQL> alter database  datafile '/opt/oracle/oradata/irdex/irdex_arch07.dbf' resize 4000m
  2  ;

Database altered

SQL> alter database  datafile '/opt/oracle/oradata/irdex/irdex_arch08.dbf' resize 400m;

Database altered

SQL>