The Point-in-Time Copy feature, which includes FlashCopy, enables you to create full volume copies of data in a storage unit. When you set up a FlashCopy operation, a relationship is established between the source and target volumes, and a bitmap of the source volume is created. Once this relationship and bitmap are created, the target volume can be accessed as though all the data had been physically copied. While a relationship between the source and target volume exists, optionally, a background process copies the tracks from the source to the target volume.

When a FlashCopy operation is invoked, it takes only a few seconds to complete the process of establishing the FlashCopy pair and creating the necessary control bitmaps. Thereafter, you have access to a point-in-time copy of the source volume. As soon as the pair has been established, you can read and write to both the source and target volumes. Figure 1-1 illustrates the functionality of DS8000 FlashCopy.

The background copy may have a slight impact to your application because the physical copy needs some storage resources, but the impact is minimal because the host I/O is prior to the background copy. And if you want, you can issue FlashCopy with the no background copy option.

Figure 1-1 FlashCopy provides a point-in-time copy

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