We tried to make OpenKM as intuitive as possible, but an advice is always welcome.
Forum rules: Please, before asking something see the documentation wiki or use the search feature of the forum. And remember we don't have a crystal ball or mental readers, so if you post about an issue tell us which OpenKM are you using and also the browser and operating system version. For more info read How to Report Bugs Effectively.
The SDK for Java and OpenKM have been tested for files at least of 2GB, I think the problem should not be in the SDK. Anyway, tell us your OpenKM version and a small sample code to check as similar as possible.