How to fix drop table and truncate table commands frozen in Oracle 10g
Read Oracle expert Brian Peasland's explanation of why drop table and truncate table commands may be frozen in Oracle 10g.
On my website is a white paper titled Solving User Problems. Page 3 discusses how to find the SID for your session. Once you've identified the SID of the session that is having the difficulty, then look to pages 6-8 to see if another session is holding a lock. If there is no lock, then look to pages 15-17 to see what wait events are holding up the session.