To avoid any significant impact on performance because of multiple targets, FlashCopy  creates dependencies between the targets. Dependencies can be considered as “hidden”  FlashCopy mappings that are not visible to and cannot be managed by the user. A  dependency is created between the most recent target and the previous one (in order of start  time). Figure 11-13 shows an example of a source volume with three targets. When the three targets are started, Target T0 was started first and considered the “oldest.”  Target T1 was started next and is considered “next oldest,” and finally, Target T2 was started  last and considered the “most recent” or “newest.” The “next oldest” target for T2 is T1. The  “next oldest” target for T1 is T0. T1 is newer than T2, and T0 is newer than T1.  No specific behavior is shown for read operations on source volumes when multiple targets  exist for that volume. The data is always read from the source. A write to the source volume does not cause its data to be copied to all of the targets. Instead,  it is copied to the most recent target volume only. For example, consider the sequence of  events that are listed in Table 11-3 for a source volume and three targets started at different  times. In this example, no background copy exists. The “most recent” target is indicated with  an asterisk. Chapter 11. Advanced Copy Services  479 Table 11-3 Sequence example of write IOs on a source with multiple targets Figure 11-13 FlashCopy dependencies example Source read with multiple target FlashCopy Source write with multiple target FlashCopy (Copy on Write) Source volume Target T0 Target T1 Target T2 Time 0: mapping with T0  is started A B C D E F _ _ _* _ _ _ Not started Not started Time 1: change of “A” is made on source (->“G”) G B C D E F A _ _* _ _ _ Not started Not started Time 2: mapping with T1  is started G B C D E F A _ _ _ _ _ _ _ _* _ _ _ Not started