How to fix a buffer in main memory, without going to swap.

[Arturo Puente]

 I am posting this for helping a friend:

 "I have a big buffer of size N, with N less than the main memory of my
  workstation. I want to have the buffer all time in main memory, without
  going to swap space. Is there some UNIX system call than can do this.?
  Is there another form to do this.?"

  Thank you in advance for your help.

  Arturo Puente