Peformance degradation

We have recently completed a database reorganisation of our Online 5.04 system. Immediately after the re-org, we had significant improvements. However, the following day the performance has slumped again. We sized the table extents well and we have no problems with buffers. Both read and write cache percentages are over 95%. We thought that our original problem with performance was releated to extent fragmentation, but this does not seem to be the case. Is it fragmentation within the extents that is causing the problem? We did the reorganisation mentioned above in the hope that we would not have to remove the striping from our disks. The striping prevents us from doing much in the way of seperating tables and means that we are sharing the database chunk with other non-Informix data. Could the striping be undoing our defragmentation efforts? Another thing that I noticed was that, when we are inserting into the correctly sized tables - the performance is ok. When we tried to unload or delete - the performance was terrible. I am considering suggesting to my employers that we get rid of the striping, but will this help? Does anyone have any other ideas - things to check-out? Thanks for your consideration and time.