If there is a page fault happened,OS will take page replacement to solve it.

Step1: Find the location of the desired page on the disk.

Step2: Find a free frame:

a:If there is a free frame,use it.

b.If there is no free frame,use a page-placement algorithm to select a victim frame.

c.Write the victim frame to the disk;change the page and frame tables accordingly.

Step3: Read the desired page into the newly freed frame;change the page and frame tables.

Step4: Restart the user process.