In article <[log in to unmask]>,, #Rudi Grom (aka rudigrom) says... > >As we realized in our department there is a problem with a master-dataset : >More than 20% of all entries belong to entries where the hashing-algorithm had >to calculate a secondary key-entry. Due to that the performance is very bad. >The master-dataset is 50% full. Is there a way to optimize the dataset-filling >? How does the hashing-algorithm work ? (I know there must be an article >describing it ) > 20% secondaries is not a big problem. 40% is bad, but 20% is alright. The IMAGE hasning algorithm cannot guarantee that there will not be significant numbers of secondaries at any given (realistic) dataset capacity. I guess if your dset was 1% full, you would eliminate secondaries, but that's not realistic. The hashing algorithm is described in "Primary Address Calculation" in the TurboIMAGE/XL Database Management System. Different algorithms are used depending on what data type (X, I, J, U, etc) is being used for the key value. It gives general guidelines to follow to reduce the possibility of excessive secondaries. BTW, how did you know you have 20% secondaries? If you have HOWMESSY from Robelle there is a statistic called Max Blocks which is the measure of how far the farthest secondary is away from its primary. It directly correlates to how many physical I/Os will be necessary to retrieve that secondary. I once had a large master whose Max Blocks was over 9200!!!!! Needless to say we resized immediately. A Max Blocks of 5 or less is completely livable. IN any case, you may want to explore other reasons your database or application seems slow. 20% secondaries should not cause a huge problem, at least in my experience. >Regards Rudi > -- Mark Landin System Manager Superstar Satellite Entertainment [log in to unmask]