I looked at ProIV's documentation regarding creating memory files (topic ID 720293) and it has left me more confused than enlightened.
I took the simple approach of changing the file type of one of our existing "working files" and regenning all functions that reference it. It seems to have made no difference at all in execution speed of the report I was testing. The documentation also mentions adding an entry to pro4v7.ini which I did but it still makes no difference.
Chaging to mem file is quite simple - sounds like you did it correctly. with modern file systems there is a lot of caching going on - if this was a pro-isam or c-isam file originally then converting to mem file may not give as much advantage as you might think - replacing a database table based workfile can give huge performance advantages. Perhaps theres is something else slowing your report? What sort of volume of data were you processing using this memory workfile? I'm quite sure if you really pump up the volume you will see a difference.