Your thread doesn't contain much details about settings, portingset etc. but hereby some tips:
- Try to find out if locking occurs. Does the problem also occur on an empty system?
- Read the manual on top of this group to find how to find long running queries (BLAT, DB2PROF).
- Investigate if DB2/400 has been tuned.
BTW: this post has been made on my personal view. My employer might not share my point of view.