"Out of memory" (OOM) is an error message seen when a computer no longer has any spare memory to allocate to programs. An out of memory error causes programs — or even the entire computer — to power down. This problem is typically caused either by low random access memory (RAM), too many programs or hardware pieces running at once, or a large cache size that absorbs a large amount of memory. Some people erroneously believe that deleting items from the hard drive will alleviate this problem, but doing so does not lower the amount of RAM being used.
The error means the computer no longer has any spare virtual memory for programs or hardware. To make room for this memory, the computer will often forcibly shut down programs and, possibly, the entire computer. This memory typically is allocated to programs, but memory and power are also needed to make hardware such as speakers work.
One of the most typical reasons for receiving this error message is due to low RAM. The system does not have much memory to use for operations, which makes it run out of memory quickly. This is especially true when programs such as games, which need a lot of resources, are running. Even computers with moderate amounts of RAM may encounter this problem if several programs and hardware pieces are being used simultaneously.
Computers that have high amounts of RAM may also encounter this problem, and while many programs running simultaneously might be the problem, computers with high RAM run into a different problem. When a computer boots up, it assesses the amount of available RAM and creates a cache. The cache itself takes up memory. With computers that have high amounts of memory, the cache can take up a substantial amount of memory, causing the out of memory error.
Fixing this problem is usually easy. Shut down any programs that are not necessary to free up resources. At the same time, check the computer’s status window to ensure it has freed up the resources, because the computer may not make the RAM available for several minutes. Restarting the computer is the easiest way to ensure all the resources are free. RAM size can also be upgraded by purchasing and installing new RAM chips.
Some people believe the error message refers to the memory in the hard drive, because both RAM and hard drive space are casually referred to as memory. Following this, these people will start deleting files from the computer to free up memory. While it will thin out the hard drive, this will not fix the out of memory error.