OpenEdge bypasses operating system buffers with the use of –directio, limiting the need for operating system buffers. Operating system buffers are still used for temporary file I/O for any client processes that reside on that machine. Most operating system manufacturers allow you to modify the number of buffers that can be allocated to the operating system. If you are using the -directio startup option, then you can reduce the amount of operating system buffers to approximately 10 percent in most cases. One major exception is systems with very limited memory (less than 256MB), where leaving the parameter at its default value is the best practice.