We had some problems about VMC and it's bottleneck some time ago, I'm not sure if is exactly your scenario but this information may help you. Our solution was about find a balance between system settings and the custom code, you can have some control on that if udpate is done inside a RFC or as a background job, this will generate a new LUW which will get destroyed once the update is finished, so the memory will be released. In our scenario we have a massive processing, so I used RFC to get adavantage of the process paralelization to speed it up plus avoid VMC bottlenecks, but even with that your basis team should check if VMC values are set according to the SAP recommendations, you can find some note which explains that and which rules you should apply to size it correclty, it's not easy stuff.
Cheers!
Luis