Coalescing tablespace free space and EVENTS

I think this was posted and answered in this newsgroup some time back but I was unable to find the relevant articles in my Netscape News-reader. So, please bear with me and post your replies or mail directly to me.

o How do I use ALTER SESSION SET EVENTS '.....'; to coalesce the free space in my tablespace on demand without waiting for SMON to do it?
 I tried to do it as
ALTER SESSION SET EVENTS 'IMMEDIATE TRACE NAME COALESCE 7'; where 7 is my TS# in SYS.TS$ and I got the following error
"ORA-2194 event specification syntax error 230 (minor error 214) near '7'

o On a more general note, what are the various 'EVENTS' that I can use in my ALTER SESSION command to trace/debug/force certain events/simulate certain situations?   I know that I can also put these events in my init.ora file as
EVENT=".......". I would appreciate any feedback/comments/help.

Thank you,
--Vikas Agnihotri
  vikas_at_mink.att.com Received on Fri May 10 1996 - 00:00:00 CEST