Swapping is the process of exchanging memory pages between main memory and secondary storage, such as a hard disk. There are three types of swapping that occur. When memory becomes full, inactive processes are swapped out to disk to free up space, and are swapped back in when needed. The first UNIX systems constantly monitored free memory and swapped out processes to disk when levels fell below a threshold. Swap space is used on Linux when RAM is full, with inactive memory pages moved to the swap file to free up space. The swap cache helps avoid race conditions when processes access pages being swapped by collecting shared pages that have been copied to swap space.

2. Swapping is the process of exchanging pages, segment of memory and values
to another location. It occurs in three types.
 A process can be swapped temporarily out of memory to a backing store, and
then brought back into memory for continued execution, here backing store is
the fast disk large enough to accommodate copies of all memory images for all
users and must provide direct access to these memory images.
The first UNIX system kernels monitored the amount of free memory
constantly. When it became less than a fixed threshold, they performed some
swapping out. This activity consisted of copying the entire address space of a
process to disk. Conversely, when the scheduling algorithm selected a swapped
– out process, the whole process was swapped in from disk.

3. Swapping in OS

4. Swapping in Linux

5.  Swap space in Linux is used when the amount of physical memory
(RAM) is full. If the system needs more memory resources and the RAM is
full, inactive pages in memory are moved to the swap space. While swap
space can help machines with a small amount of RAM, it should not be
considered a replacement for more RAM.
 The swap cache is crucial to avoid race conditions among processes
trying to access pages that are being swapped. The swap cache collects
shared page frames that have been copied to swap areas. It does not exist
as a data structure on its own; instead, the pages in the regular page
cache are considered to be in swap cache if certain fields are set.

6. Swap area

7. Swap cache

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