If the reference was invalid, the process is terminated. Otherwise, the page must be paged in.

A free frame is located, possibly from a free-frame list.

A disk operation is scheduled to bring in the necessary page from disk. ( This will usually block the process on an I/O wait, allowing some other process to use the CPU in the meantime. )

When the I/O operation is complete, the process’s page table is updated with the new frame number, and the invalid bit is changed to indicate that this is now a valid page reference.