Fragmented disk

In this scenario the disk is badly fragmented with lots of small areas of free space, which allows some requests to be satisfied.

Scenario 2 - A badly fragmented disk.

As on an earlier page the request for disk space was:

//ddname DD SPACE=(CYL,(15,5))

Even though the free space is only available in many small areas, if the amount of data exceeds the capacity of the initial request of 15 cylinders, then the potential disk space available could be:

Request	Extents	Allocation
15	5	15 (3 * 5) Cylinders for Primary
5	10	10 (1 * 10) Cylinders for Secondary
	----	---------------------------------
	15	25 Cylinders across 15 extents

The secondary request amount is saved in the F1 DSCB, allowing the value to be used to extend the data set at a later time.

This allocation is illustrated on the next page.