Example 3

In example 3, the area to be referenced does not begin on a page boundary. The reference pattern includes a reference unit of 2000 bytes and a gap of 5000 bytes. When you specify a reference pattern that includes a gap, the reference unit must be at the start of the area, as the following illustration shows:

Because the gap is larger than 4096 bytes, some pages do not come into central storage. Notice that the system does not bring in the fifth page.

Summary of how the size of the gap affects the number of pages the system brings into central storage:

If the gap is less than 4096 bytes, the system has to bring into central all pages of the array.
If the gap is greater than 4095 bytes and less than 8192, the system might not have to bring in certain pages. Pages that contain only data in the gap do not come in.
If the gap is greater than 8191 bytes, the system definitely does not have to bring in certain pages that contain the gap.