Hello All, I have a question concerning Reblocking an automatic dataset and performance. In everything I have read and heard (and it certainly makes sense to me...) is that reblocking has no affect on performace on the new RISC HP3000 machines - only disc space usage. This is due to the fact that the Operating System no longer fetches data at the block level and now fetches at the page level. A page can contain several blocks. I have an automatic that is getting "messy". Here is the output from Robelle's Howmessy Report: HowMessy/XL (Version 2.5) Data Base: CLMSDB for IMAGE/3000 databases By Robelle Consulting Ltd. Secon- Max Type Load daries Blks Blk Data Set Capacity Entries Factor (Highwater) Fact AC-CLAIM-NUMBERS Ato 7993157 3524898 44.1% 41.0% 5192 2 Max Ave Std Expd Avg Ineff Elong- Chain Chain Dev Blocks Blocks Ptrs ation 95 1.70 2.37 1.24 3.17 88.8% 2.55 Increasing the capacity should help cure the high percentage of secondaries by better hashing , which it did, but at at a 30% load factor only helped bring down the secondaries to 36%. At this capacity, this increased the size of the dataset by a few million sectors - a high price to pay for only 5% reduction in secondaries. So, I'm accepting the fact that I have a not so great hashing key and will have a high percentage of secondaries. I left the capacity at its original 44% load factor. Changing the key is not an option. My strategy now is to just make sure there is minumum I/O when reading the synonym chains by having them already fetched into memory. As A. Rego says, "There are 'good' secondaries and 'bad' secondaries". Despite what I have read, I decided to experiment with the blocking factor. This automatic has a media length of 63, so my maximum blocking factor is 40 given a buffer length of 2560. I will have around 40 bytes of wasted per block, but I decided to give it a try anyway. To my surprise, this automatic started looking much better - "Max Blocks" went down severely which will help my "DBPUT" performace - "Inefficient Pointers" decreased by half which should help my "DBGET"/"DBDELETE" performance - "Elongation" went down also. Here is the output after reblocking: HowMessy/XL (Version 2.5) Data Base: CLMSDB for IMAGE/3000 databases By Robelle Secon- Max Type Load daries Blks Blk Data Set Capacity Entries Factor (Highwater) Fact AC-CLAIM-NUMBERS Ato 7993157 3524898 44.1% 41.0% 258 40 Max Ave Std Expd Avg Ineff Elong- Chain Chain Dev Blocks Blocks Ptrs ation 95 1.70 2.37 1.00 1.97 39.6% 1.97 I then decided to Repack this automatic physically putting all synonym chains together. Things even looked better now. "Max Blocks" decreased - "Inefficient Pointers" decreased by half again - and "Elongation" decreased. Here is the output after Repacking: HowMessy/XL (Version 2.5) Data Base: CLMSDB for IMAGE/3000 databases By Robelle Secon- Max Type Load daries Blks Blk Data Set Capacity Entries Factor (Highwater) Fact AC-CLAIM-NUMBERS Ato 7993157 3524898 44.1% 41.0% 150 40 Max Ave Std Expd Avg Ineff Elong- Chain Chain Dev Blocks Blocks Ptrs ation 95 1.70 2.37 1.00 1.48 19.5% 1.48 THE MAIN QUESTIONS: Comparing this final "Howmessy" report to the first, there is a vast improvement which should yeild greater performace. Is this the case though? Despite these improvements, is the performance not going to increase? Is fetching at the page level so large that all of my synonym chains are already in memory and reblocking has no affect? If so, should I not be concerned with Ineffcient Pointers and Elongation for automatics? Any help is greatly appreciated! Thanks for your time in reading this long posting! - Dave Geis DBA Humana/ ChoiceCare * To join/leave the list, search archives, change list settings, * * etc., please visit http://raven.utc.edu/archives/hp3000-l.html *