I believe what your DBA is referring to is known as SAFE (Simple Algorithm for Fragmentation Elimination), available as a whitepaper on metalink at http://metalink.oracle.com/cgi-bin/c..._cr.cgi?239049

The idea is to keep uniform extent sizes in tablespaces and move objects as they approach a given threshold (512 extents, 1024, whatever) to a tablespace with larger extents.

I believe the aim is lower fragmentation rather than improved performance, although some would argue it is a means to the end. Also, no need to coalesce tablespace, and so on.

Hope this helps.

Dave