Workitem archive performance gone to the dogs!

[K Keir]

We've had the archive object 'workitem' running in production for a while now
(abap = rswwarca).  Performance started out ok (i.e. 179,000 items took 4
hours), but has now deteriorated to unacceptable ... (takes days!!).
 
These are almost all type 'C' items.   We have looked at and tried various OSS
notes without success.  One note
153205 says to create a new abap RSWWCIDE in place of RSWWWIDE/RSWWHIDE.   Has
anyone done this or have any other ideas - I'm concerned as we were told that
RSWWWIDE should not run in a prod environment (you should always use RSWWARCA).?
 
We are on 4.0B  and DB2.