In page replacement
Page replacement:-
In a computer operating system that uses paging for virtual memory management, page replacement algorithms decide which memory pages to page out, sometimes called swap out, or write to disk, when a page of memory needs to be allocated.
If there is a free frame, use it. If there is no free frame, use a page-replacement algorithm to select any existing frame to be replaced, such frame is known as victim frame.
Frame is free by writing contents to swap space and changing the page table to indicate that the page is no longer in memory.
The free frame can now be used to hold the page for which the process faulted.