How complicated could be a fragmentation expression?

Hi "Performance Guide" - in the chapter on fragmentaton strategies - says: "Fragmentation expressions can be as complex as you want. However, complex expressions take more time to evaluate and might prevent fragments from being eliminated from queries" I wonder if expressions like: mod(field_x,103) between 0 and 30 field_a=x and field_b = y or field_a=z mod(field_x,103) in (a lot of values) are the kind of complex expression they are talking about. Usually I would choose a simpler expression (for example mod (field, one_digit) = x) but if I do so rows are not balanced across fragments. Should I choose the complex expression hoping performance won't be too decreased or should I use the simple one and deal with the uneven distribution? My other alternative would be using round-robin, but since database is an OLTP one, I should create detached indexes elsewhere. In such case, my question is: should I fragment indexes in order to improve searchs (Table has 28M rows and increasing) or it's better put entire indexes in a separate disk as guide says? Thanks in advance Omar Mu'oz ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ