:I have a program that processes a file of 500,000+ records which runs very slow. Each record chains to a another file to see if a record exists and does some calcs. Out of the total master file, there would be no more than 1000 successful hits on the secondary 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?