Performance tuning SELECTs: Can I force a TRUE db read every time?

Good day everyone!

I've been programming in ABAP for almost 6 years now, and I'd like to begin learning more about performance tuning with respect to database performance.

More specifically, I'm testing some things in a particular SELECT in a report program we have that is timing out in the foreground because of the SELECT. When I first run the program, the SELECT goes against the database, as we all know. Subsequent runs, however, use the buffered data, so the response is a lot quicker and doesn't really reflect that first, initial database read.

Am I correct in assuming that I should be testing my various approaches and collecting performance runtimes against that initial, "true" database read? If that's the case, is there any way I can force the system to actually read the database instead of the buffered data? For those experienced with this kind of performance analysis and tuning, what's the best approach for someone very new to this area such as myself?

Thank you,

Dave