I only make this comment because I notice that the 1.6.2 release of UMS for Windows promotes usage of the 1.7.0 u 21 Java VM. I find that u 21 has made significant changes to GC policy and as such, even if I double my max heap limit (to -Xmx1536M) I am unable to complete a scan of my media without Out of Heap Memory exceptions. This applies to 1.6.1 and 1.6.2 releases. The u 15 Java VM (from which I upgraded on this system) appears to have a more rapid GC cycle (or just a different policy) and completes my media scan with a 768M max heap. This may be Linux/32 bit only of course.
I will look at the Java bug parade at some point to see if this is already understood. There have been several alternative GC policies introduced into Java 7, it may be that the default variant has changed or that some tuning has occurred.
Any help will be apprecited.
I didn't find the right solution from the Internet.