(Q) Chained rows/LONG & Deletes

Hey all,

I have a 7.3.4.5 database. There are 15 tables with LONG datatypes in them. The average size of these tables is ~40G. Total rowcounts in them are around 50 mill. These are OLTP tables with a LOT of updates going on.

Fortunately, we purge out records > 30 days old. We have gotten some small increases in the number of inserts lately, and these tables are starting to grow. Of course, since LONGs are notorious for chaining, I have a heck of a lot of chained rows in these tables. This is naturally causing performance degradation and rapid growth.

My question is this:
How does Oracle move the LONG chained block information to the freelist? Are all the blocks for these chained rows (under the HWM) able to be reused in the future?

I want to make sure I choose the correct way to improve performance in this case. Imp/Exp is one way to alleviate the problem. I could create a temp table and move the chained rows to the new table, delete and move them back. I can also fiddle with pctfree/pctused to try to get 1 row/block. (which seems inefficient at best, and nightmarishly space wasting at worst)

Also, does anyone have a better way (other than dba_segments, dba_free_space and dbms_space) to see how much space is truly being wasted by these chained LONGS? (the reason I say better is because I can't really tell how much space is being wasted by a chained LONG by looking at any of the standard views)

TIA,

--
cr