Virtual Memory (or) Swap Space

Unix supports virtual memory, which is, using a category of the hard disk as an extension of RAM so in which the effective size of usable memory grows respectively. The kernel will write the contents of a not-right- now used category of memory to the hard disk so in which the memory can be used for another purpose. Whenever the actual contents are required again, they are read back within memory (not necessarily to the similar place). This is all done transparent to the user; a programs running under Unix only see the huge amount of memory available and do not notice in which categories of them reside on the hard disk from time to time. Certainly, reading and writing the hard disk is slower (on the order of a thousand times slower) than using the real memory, so the programs do not run fast. The category of the hard disk in which it is used as virtual memory (as this is called) is known as the swap space.

Adding More Swap Space

As system configuration modifies and new software packages are installed more swap space may have to be added. The ideal way to add swap is through using the touch and mkswap, this commands to designate a port on an existing file system.