Node-RED and memory

You don't allocate memory to node. Node asks the OS for memory when it needs it. You hit OutOfMemory when the OS is unable to allocate any more memory.

If you are trying to process thousands of files using NR then it sounds like you're trying to do too much at once. How does the flow operate? Have you built any throttling in or is your flow trying to handle the thousands of files in one go?