Find Minimum size of datafiles for resize operations in TOAD
Last minute addition!
If you are not happy with the response times, you may try gathering dictionary statistics, it helped me a lot that response times decreased from minutes to seconds.
exec DBMS_STATS.GATHER_DICTIONARY_STATS;
If you had exhausted of space, and tried to find a quick way of resizing the tablespaces. You may want to use TOAD feature:
From Administer ->Tablespaces-> Select one tablespace and press F4. In the opened window click datafiles tab and double click the datafile which you want to resize. In this window there is a button “Minimum Size?”, click it.
After some time of processing, it will find the minimum size of datafile it could be, it could be better than trial-error method for exact sizes.
Tablespace Menu Selection
Datafile Definition Window
Derya Oktay's Weblog 
which version of TOAD has this resize feature?
Hi Thuhong,
As far as I know it is existing nearly in all versions. At least from TOAD 6.
You may not see this feature because, your TOAD license does not cover Admin Module license.
I will also add the picture of the feature.
Derya.