... To make this translation easier, virtual and physical memory are divided into handy sized chunks called pages . ... The physical page frame number that this entry is describing, . ... As the physical page frame number for a given virtual page of System V shared memory is contained in the page tables of all of the processes sharing this area of virtual memory, the kernel swap daemon must modify all of these page tables to show that the page is no longer in memory but is now held in the swap file. ...