RMS_TUNE_CHECK

RMS Performance: Duplicate key chains

Hein van den Heuvel

Does
your application use RMS Indexed files?
Do you know what a SIDR is? Do you know what a duplicate key chain is?
You probably should, since SIDRs and duplicate key chains can cause thousands
of read I/Os as the result of a single record insert. With that, they can have
a tremendous impact not just on the application doing the insert, but also on
total system performance. Application managers, of course, notice
a slowdown over time, and all too often they solve that by throwing more
hardware at the problem. But what if you already have the biggest box on the
market? Modest file tuning and a convert can help avoid all those read I/Os and
restore performance. I have yet to investigate an RMS application that did not
have this duplicate key chain problem. Maybe this is because I get called in
only for bad cases, or because indeed so many applications have this problem,
at least to some degree.