Hi,
I am certainly not an expert on HANA's memory management. But from your picture it looks like HANA is leaking memory, which it certainly is not.
I assume that HANA is not giving back the memory the the OS because it may reuse it later on. But HANA doesn't forget about this memory for sure. That's actually a very common pattern, which nearly all applications written in C/C++ use. The ABAP does similar things at many occasions.
Best regards,
Kilian.