We are running a simplish Acu9.2 database, and one of our clients has a large database with about 1 million entries. The files are split since they're so big. Since upgrading to Server 2019 we have noticed a strange performance behaviour that's completely reproducible.

If we run REPORTA which goes through all the data and pulls out certain records, on the first run after reboot/login it takes in excess of 1 hour. If I then run the same report again it's over 10 times faster. 

If we run REPORTA , on the first run after after login it takes an hour then I logout and into our application again, and run the same report but with different parameters, it's also 10 times faster ie. about 6 minutes.  I can see it scrolling through the records much faster.

What's going on here, and can I make it faster on the first run? I know I should be upgrading to Acu 10 and rekeying the database, but let's assume that's all impossible 

It looks like some kind of OS caching going on, but that wouldn't  explain such a vast difference. 

For the first issue, ReportA on startup of server I would make sure the Anti-virus software isn't scanning the data or data directories. The next aspect worth looking into is, how is the Vision file arranged, meaning are you reading by the 2nd key when the file is built based on the first key. This could explain issue #2 as well, that even though you change parameters in the report, the reports got run once, arranging the file based on a certain keys and even though your parameters changed, the reads are simply faster now that the file has be ordered by the first execution.