text: FlashCopy mappings can be part of a Consistency Group, even if there is only one mapping 
  in the Consistency Group. If a FlashCopy mapping is not part of any Consistency Group, it is 
  referred as*stand-alone*. 
  
  **Dependent writes**
  It is crucial to use Consistency Groups when a data set spans multiple volumes. Consider the 
  following typical sequence of writes for a database update transaction: 
  
  1. A write is run to update the database log, which indicates that a database update is about 
  to be performed. 
  
  2. A second write is run to perform the actual update to the database. 
  
  3. A third write is run to update the database log, which indicates that the database update 
  completed successfully. 
  
  The database ensures the correct ordering of these writes by waiting for each step to 
  complete before the next step is started. However, if the database log (updates 1 and 3) and 
  the database (update 2) are on separate volumes, it is possible for the FlashCopy of the 
  database volume to occur before the FlashCopy of the database log. This sequence can 
  result in the target volumes seeing writes 1 and 3, but not 2 because the FlashCopy of the 
  database volume occurred before the write was completed. 