Morning Chris, > Mark - I think Jonathan hinted at what you're saying about the clustering > factor but I'm "new" to this detailed analysis using 10053 so I'm behind you > guys in regard to how clustering factors, NDVs, random fetches, et.al all > play/fit together. I'm trying to come up to speed on it now - hence this > thread. Tom Kyte's article in the latest Oracle magazine is online and covers, id excellent detail and clarity, index clustering factors. You can read it at http://www.oracle.com/technetwork/issue-archive/2012/12-sep/o52asktom-1735913.html HTH Cheers, Norm. -- Norman Dunbar Dunbar IT Consultants Ltd Registered address: Thorpe House 61 Richardshaw Lane Pudsey West Yorkshire United Kingdom LS28 7EL Company Number: 05132767 -- //www.freelists.org/webpage/oracle-l