RE: Setll vs. chain

Carl wrote:

>We have a report program that processes a master file 
>of 300,000+ records which runs ever so slow.  Each 
>record chains to a formula file to see if a formula exists 
>and does some calcs. Out of the total master file, there
>would be no more than 1000 successful hits on the 
>formula file.  Before I go ripping this code apart (and 
>converting it to RPGIV in the process), my expectation 
>is that if I change the CHAIN to a SETLL and then chain 
>on a successful hit that it should improve the performance 
>considerably.  Am I wrong in assuming that SETLL will 
>just look at the "index" which should be in memory as 
>opposed to CHAIN which most often requires an access 
>to disk to retrieve the record? TIA.

The "classic" answer to this sort of problem is to turn it on it's head.
Assuming that the formula file has far fewer records than the master file,
read the formula file then SETLL/READE the corresponding master records.  I
would bet that simply changing CHAIN to SETLL will not buy you anything
because of the large number of "no hits" - CHAIN won't transfer data anyway
in this scenario.  If you need to sort on some field in MASTER, strongly
consider creating a join logical/OPNQRYF/SQL.

Buck Calabro
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