Reclaim space from DBFs

Question

Hi All,
I have one query regarding tablespace reclaim space. I have users tablespace which is having 5 dbfs. Some of the DBFs of USERS tablespace having autoextend on with max size 32G and some of the DBFs not having autoextend on and maxsize 4G.
Now when I checked the USERS TBS through EM , I come to know only few MBs out of 20G are in used in 3 DBFs of USERS tablespace and rest of 2 dbfs are in good in use. Now I want to reclaim the space from 3 dbfs say users03,users04 and users05. users01 and users02 are properly in used. I want to reclaim the space from 03,04 and 05.
can I have any idea how to reclaim space from dbfs? I try with alter database datafile ...resize but giving error "ORA-03297: file contains used data beyond requested RESIZE value".
please suggest me,
Thanks...

Answer 1

Yes, I think you are understanding how it works. For a visual example, if this is your data file:
XXXX--XX-XXXX-XXXX-XXXX-XXXXXXX-----------------
and you delete some data
XX----X--------X------------------X-----------------
The datafile can be resized only down to
XX----X--------X------------------X
Which tools are available to do this efficiently vary by database version, for example in my 9.2.0.6 database I can use exp/imp, CREATE TABLE AS SELECT, rebuild indexes (mostly) online, exp/imp, move LOBs around with ALTER TABLE ... MOVE LOB, or other strategies - some of these are more work than others, and all will take some amount of time. In 8i There are fewer options; beginning with 10g data pump and DBMS_REDEFINITION are available; in 11g the index rebuilds don't lock the data, so the time may be less of a concern.
Before you even spend the time to shrink these data files, consider the space needs for USERS. If the extended size was a one-time thing, then shrinking datafiles may be justified. If USERS may grow that large again then a data file shrink is a lot of work for little gain.