SortMerge->HashJoin

Hello All, I have a query that on 5.0 is doing a 'sort merge', and 7.3 doing a 'dynamic hash join'. The 5.0 instance is about twice as fast. Is there a way for me to force 7.3 to do a Sort Merge? Also, I have a couple of off-topic questions: 1) If I have my physical and logical logs in the root dbspace, would this in any way effect query (no update/insert) performance? (Disregarding checkpoints) 2) Same question as above but with buffered/unbuffered logging status? Thanks for any time and feedback. Olaf