Hi Andre,

It’s probably out of scope to give a reasonable response to your questions via the public mailing list (feel free to ask for our commercial services), but here’s a quick shot:
  • why is the whole database read even for a "small" query ? (looks like a missing index or bad execution plan.. ?)
It may depend a lot on what the query does. Could you give us an example for a typical “small query”?
    • The UNIX related question (maybe it's worth opening a ticket with redhat)
I guess so. I’m sorry I have no in-depth knowledge on why RHL 6 and 8 behaves differently here.

Have you already tried different JDK versions/distributions?

Best,
Christian