Aspects of the invention include receiving, at an operating system executing on a processor, a write request from a program to write data to a memory. The write request includes a virtual memory address and the data. It is determined that the virtual memory address is not assigned to a physical memory address. Based on the determining, the unassigned virtual memory address is assigned to a physical memory address in an overflow memory. The data is written to the physical memory address in the overflow memory and an indication that the write data was successfully written is returned to the program. Future requests by the program to access the virtual memory address are directed to the physical memory address in the overflow memory.