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I work in a shop that does a lot of mailing list processing that involves files with between 1 and 8 million records. Preparing a list involves a lot of updates to the information that doesn't pertain to the name and address. Our standard has been for many years sequential I/O writing the output to a clone of the input file. We generally use forced blocking with OVRDBF as well. I haven't benchmarked the process recently, but it seems to me that two machines ago, sequential I/O made the process more than twice as fast. Since the original file is ordered (not indexed) it allows comparisons with other ordered files without using random I/0 by means of a simple linear search. The really scary thing is that reading all the records in two 2 million record files can be faster than reading all the records in one and doing keyed lookup on the other. > -----Original Message----- > From: Dave Murvin [mailto:davem@drme.com] > Sent: Saturday, October 16, 1999 2:56 PM > To: RPG400-L@midrange.com > Subject: Re: Expensive op codes > > > /* Snip */ > I have been doing some testing on record blocking and reading > of large files. > Some of these tests may have been unscientific, but I think > they point the way to > go. > > All tests were run in batch on a dedicated S10. Test jobs > were the only > application running. > File being read is a keyed logical with the physical file in > the same sequence as > the key. > Number of records in file is 1,027,600 with record length of 191 > > Both test runs used OVRDBF FILE(ECLL02) SEQONLY(*YES 341) > Both test runs read the entire file by key. Program 1 used > READE, program 2 used > READ and compare. > > Program 1 elapsed time was 33 minutes 38 seconds. > Program 2 elapsed time was 12 minutes 38 seconds. > > +--- | This is the RPG/400 Mailing List! | To submit a new message, send your mail to RPG400-L@midrange.com. | To subscribe to this list send email to RPG400-L-SUB@midrange.com. | To unsubscribe from this list send email to RPG400-L-UNSUB@midrange.com. | Questions should be directed to the list owner/operator: david@midrange.com +---
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