Table 11-4 lists the indirection layer algorithm in a multi-target FlashCopy. When a mapping that contains a target that includes dependent mappings is stopped, the  mapping enters the  stopping  state. It then begins copying all grains that are uniquely held on  the target volume of the mapping that is being stopped to the next oldest mapping that is in  the copying state. The mapping remains in the  stopping  state until all grains are copied, and  then enters the  stopped  state. This mode is referred to as the  Cleaning Mode .  For example, if the mapping Source-T2 was stopped, the mapping enters the  stopping  state  while the cleaning process copies the data of T2 to T1 (next oldest). After all of the data is  copied, Source-T2 mapping enters the  stopped  state, and T1 is no longer dependent upon  T2. However, T0 remains dependent upon T1. For example, as shown in Table 11-3 on page 479, if you stop the Source-T2 mapping on  “Time 7,” then the grains that are not yet copied on T1 are copied from T2 to T1. Reading T1  is then like reading the source at the time T1 was started (“Time 2”). As another example, with Table 11-3 on page 479, if you stop the Source-T1 mapping on  “Time 8,” the grains that are not yet copied on T0 are copied from T1 to T0. Reading T0 is  then similar to reading the source at the time T0 was started (“Time 0”). If you stop the Source-T1 mapping while Source-T0 mapping and Source-T2 are still in  copying mode, the grains that are not yet copied on T0 are copied from T1 to T0 (next oldest).  T0 now depends upon T2. Your target volume is still accessible while the cleaning process is running. When the system  is operating in this mode, it is possible that host I/O operations can prevent the cleaning  process from reaching 100% if the I/O operations continue to copy new data to the target  volumes. Chapter 11. Advanced Copy Services  481 Stopping process in a multiple target FlashCopy: Cleaning Mode Table 11-4 Summary table of the FlashCopy indirection layer algorithm t Accessed  Volume Was the grain  copied? Host I/O operation Read Write Source No Read from the source  volume. Copy grain to most recently  started target for this source,  then write to the source. Yes Read from the source  volume. Write to the source volume. Target No If any newer targets exist for  this source in which this grain  was copied, read from the  oldest of these targets.  Otherwise, read from the  source. Hold the write. Check the  dependency target volumes  to see whether the grain was  copied. If the grain is not  copied to the next oldest  target for this source, copy  the grain to the next oldest  target. Then, write to the  target. Yes Read from the target volume. Write to the target volume.