Funny, QDXi 5.3 requires 1.4.1 Java for AIX wihich has been sunsetted. I’m referring to page 30 of the pre-installation instructions for AIX.
All platforms, excluding AIX, require java 1.4.2 according to the documentation.
QDXi 5.1 required 1.3 (which we have) is running fine.
